Shelly is moderately good in Brawl Ball since she can destroy the walls blocking the enemy's goal and allow your team to score more easily. A rather useful tactic some people use is shooting the ball and then immediately using her Super to break any obstacles in the way and pushing back enemies in front of the goal, which could potentially lead to a victory in said game mode.
In Duo Showdown, if you have a teammate with ranged jumps like El Primo or Edgar, you can charge your Super up and then get defeated on purpose. When you are just about to respawn, your teammate can jump near an enemy team so that you respawn next to them. Then, use your Super to eliminate them rapidly. Your immunity shield will protect you while you do this. If your teammate is a squishier Brawler like Crow, they can jump slightly further away from the enemy and you can then use her Fast Forward Gadget to get near the enemies and use the same strategy. This will result in a team-wipe as it works well regardless of the number of Power Cubes the enemy has, since the immunity shield you get after respawning for a couple seconds makes you impossible to defeat for some seconds resulting in giving you enough time to finish the team off. Be wary of Brawlers like Bull or Darryl, though, as they can charge and roll away respectively from you before you respawn.
In Duo Showdown, two useful team compositions are Shelly and Tara, or Shelly and Gene, as either of them can pull enemies into Shelly, who can finish them off with her Super.
Recommended Build
Shelly's Fast Forward Gadget is usually the worse option in certain situations and game modes. Unlike other dashing Gadget's, like Maisie or Max, Fast Forward gives Shelly no benefits, while Maisie's has a stun and Max has temporary invincibility.
Shelly's Clay Pigeons Gadget can be used directly after using her Super at mid-range. While the enemy gets knocked back, Shelly is able to hit all bullets with the longer attacks provided by the Gadget to get maximum value out of it. This is especially effective when combined with her Shell Shock Star Power, allowing Shelly to easily land even more shots and take down foes, usually getting her Super back in the process, which could help her in a later combat.
Using her Shell Shock Star Power, Shelly can slow down Brawlers that are trying to escape, allowing her and/or her teammates to catch up and eliminate them. Shelly can also slow down the entire enemy team with her Shell Shock Star Power, making way for a potential team wipe with the help of allies.In Showdown, this can be used to catch up with longer-range Brawlers if they get hit by Shelly's Super.
Shelly's Clay Pigeons Gadget channels and increases the range of her shots for a couple seconds, making it easier to charge Supers that could help in later combats. In mirror matches or against medium-range Brawlers, this can be helpful, but her Fast Forward Gadget can give Shelly more advantage. It allows her to get in close range to enemies and ambush them, potentially surprising them if she dashes from a bush. Sometimes, though, you will find yourself using Clay Pigeons in situations where an enemy on low health is out of your normal range and you need to finish them off (like when they have a lot of gems in Gem Grab or to secure a quick elimination in Bounty or Knockout, which could potentially give your team a victory).
Strategies
When using Shelly, take advantage of walls or bushes when approaching long-range Brawlers such as Colt or Rico (for Rico, try to avoid having a large assortment of walls by and behind you that he could bounce his projectiles on, which gives him an obvious advantage), since they can out of her range and take down Shelly in the open with ease. To avoid that, be careful when using her Super, as it destroys walls, which gives her an obvious disadvantage against long-ranged Brawlers like those previously mentioned.
The spread of Shelly's attacks allows her to sweep bushes and expose any enemies hiding in them without having to go inside the bush, potentially risking being defeated by a high-damage Brawler like Bull.
Shelly's Super has the ability to cancel or interrupt other Brawlers' Supers because it knocks them back. For example, she can stop Frank from using his Super if she hits him with her Super during his wind-up. This can become even more deadly by waiting in a bush and then ambushing, since the enemies won't know you're there and won't be careful when using their Super, giving you an opportunity to surprise them, stopping their Super and potentially defeating them.
If Shelly is at low health and is being chased by a Brawler, she can use her Super to knock them back and gain a bit more time to escape. This works even better if she has her Shell Shock Star Power since she can also slow them down for a few seconds. If both of these don't help or she doesn't have her Super, Shelly can also use her Fast Forward Gadget.
Other
Shelly is best in maps with lots of bushes and walls as you can hide in a bush and camp. However, be careful when using her Super, as it destroys walls and bushes, which could prove fatal to teammates or Shelly herself if they need to take cover or hide.
Similar to Colt's Super, projectiles from Shelly's Super don't pierce through walls, they disappear after breaking one. Keep this in mind if you are trying to use Shelly's Super to defeat a Brawler behind a wall, because the opponent will take less damage due to some of the shells disappearing after breaking a wall; the more walls between you and your enemy (in a scenario where the Super is aimed perfectly at the opponent), the less damage they'll take from the Super.
Shelly is an excellent counter to tanks with her Super. However, Shelly is helpless in close-quarters combat without her Super due to the tanks’ superior health and DPS, so try to have your Super charged up before facing them.
Defeating assassins with Shelly can be tricky. To defeat such Brawlers, use your Fast Forward Gadget to get closer to the long-range assassins and defeat them at close-quarters. However, this is circumvented if the respective assassin escapes, such as Stu with his Super. For close-range assassins, focus on landing your shots correctly to quickly defeat them or use her Clay Pigeons Gadget to outrange them.
Changelog
16/08/17 Shelly's reload time was increased to 1.5 seconds (from 1.25). Her main attack range was decreased to 6.67 tiles (from 7.67). Her main attack shells have a larger spread.
07/12/17 Shelly's Shell Shock Star Power was added. The health and damage statistics of all Brawlers were multiplied by 4.
16/01/18 Shelly's Shell Shock Star Power slow duration was decreased to 2.5 seconds (from 3).
21/03/18 Shelly's main attack damage was decreased to 300 (from 320) per shell. Every Brawler's movement speed was increased by 70 points, increasing Shelly's movement speed to 720 (from 650). All Brawlers' projectile speeds are increased by 9%.
21/05/18 Shelly's health was increased to 3600 (from 3200).
29/05/18 Shelly's main attack range was increased to 7.33 tiles (from 6.67).
05/12/18 Shelly and and her Bandita Shelly skin were remodeled, and the Star Shelly skin was added.
12/12/18 Star Shelly became available to every user until 01/01/19.
15/04/19 Shelly's main attack range was increased to 7.67 tiles (from 7.33). Her main attack projectile speed was increased by 5%.
11/06/19 Shelly's Shell Shock Star Power slow duration was increased to 3 seconds (from 2.5).
26/06/19 Shelly's Band-Aid Star Power was added.
29/08/19 Shelly's Band-Aid Star Power healing was decreased to 2000 (from reaching full health).
18/09/19 Shelly's Band-Aid Star Power healing was decreased to 1800 (from 2000).
23/10/19 Shelly's animations were reworked.
24/10/19 The Witch Shelly skin was added. It was featured as a Brawl-o-ween skin.
17/03/20 Shelly's Fast Forward Gadget was added.
19/03/20 The PSG Shelly skin was unlockable by winning the PSG Cup 2020 in-game Challenge.
02/07/20 Shelly, Star Shelly, and PSG Shelly received facial animations. Shelly's True Silver and True Gold skins were added.
09/09/20 Shelly's Clay Pigeons Gadget was added.
10/09/20 Shelly's health was increased to 3800 (from 3600). The number of hits necessary to charge Shelly's Super was decreased to 2 hits (from 3). Her Super recharge rate was decreased slightly.
15/12/20 Shelly's Shell Shock Star Power slow duration was increased to 4 seconds (from 3). Shelly's Band-Aid Star Power now charges in 15 seconds (from 20).
27/01/21 Bandita Shelly and Witch Shelly received facial animations.
19/05/21 Shelly's Fast Forward Gadget range was increased to 3.33 tiles (from 3). Her Shell Shock Star Power slow duration was increased to 4.5 seconds (from 4). Her Band-Aid Star Power healing was increased to 2000 (from 1800).
16/06/21 Shelly’s Clay Pigeons Gadget projectile speed was increased by 20%.
09/07/21 Shelly's Latin America Master League skins were added.
25/08/21 Shelly's Clay Pigeons Gadget was reworked from affecting Shelly's next attack to increase her range for her attack for the next 5 seconds.
30/08/21 The Princess Shelly skin was added. It was featured as a Brawl Pass Season 8 exclusive skin.
27/10/21 Shelly's class was changed to Damage Dealer (From Fighter).
29/06/22 Shelly's Fast Forward Gadget visual effects were slightly reworked.
24/12/22 The Classic Shelly skin became available for every user to claim until 02/01/23.
25/04/23 Shelly's movement speed was increased to 820 (from 720).
06/06/23 Shelly's health was decreased to 3700 (from 3800). Shelly's Shell Shock Star Power slow duration was decreased to 2 seconds (from 4.5).
15/08/23 Shelly's movement speed was decreased to 770 (from 820).
05/09/23 All Brawlers' health and damage were increased from 5% to 10% with each Power Level. Shelly's Double Barrel Hypercharge can be obtained by completing a special quest required to win 25 matches in Hypercharge Unleashed until 11/09/23.
24/10/23 Shelly's Super recharge rate was decreased by 46%. Shelly's Band-Aid Star Power healing was decreased to 1998 (from 2000) but now scales with Power Levels. Shelly's flavor text was changed from "Shelly's spread-fire shotgun blasts the other team with buckshot. Her Super destroys cover and keeps her opponents at a distance!" to "Shelly's the perfect ranger: reliable, tough, and terrific with her shotgun. She never understood why Colt got to steal the limelight..."
27/10/23 The Hoot Hoot Shelly skin was added. It was featured as a Brawl-o-ween skin.
12/12/23 Shelly was slightly remodeled.
27/02/24 Shelly's Double Barrel Hypercharge shield boost was increased to 25% (from 15%). Shelly's Double Barrel Hypercharge multiplier was decreased to 30% (from 40%). Shelly's Double Barrel Hypercharge damage boost was decreased to 5% (from 25%). All Brawlers' Hypercharges duration can no longer be extended. Shelly was slightly remodeled.
07/03/24 The Shelly Dancer, Shelly Dancer Iris, and Shelly Dancer Dahlia skins were added. They were featured as Brawl Pass Season 24 exclusive skins and Sands of Time skins.