Trina

A Burst stage 2 (B2) Supporter who strongly boosts one Electric Assault Rifle, and as a Clip Rocket Launcher she fills Burst Gauge quickly.
Peaceful Tree2 and Mother ForestB are tuned to Electric Assault Rifle allies and Full Burst timing, so her value is high when the right Nikke fills that slot.
Without an Electric Assault Rifle DPS, she is left mostly with healing and ATK, losing much of her buff.

Peaceful Tree2, only if she is alive at battle start, grants all Electric Assault Rifle allies a lasting max-HP-only increase based on caster's max HP. At battle start, it grants 2 seconds of invincibility to the leftmost Electric Assault Rifle ally in the squad. Each time she uses her Burst Skill, it grants the leftmost Electric Assault Rifle ally increased attack damage and increased Reload Speed for 10 seconds.

Nature's Grace1, when Full Burst Time ends, grants all allies healing over time based on the caster's final max HP every 1 second for 5 seconds. When she uses a Full Charge attack, if the two allies with the lowest remaining HP ratio are at 30% or lower and 50% or lower respectively, it heals them based on the caster's final max HP.

Mother ForestB grants all allies a max-HP-only increase based on caster's max HP and increased attack damage for 10 seconds. If only one enemy remains excluding Nikkes, it applies Spreading Roots to all allies, raising damage of Burst Skills whose target description ends with all enemies. With two or more, Spreading Roots becomes Withered Roots, granting the same kind of Burst Skill damage increase at a lower value. It grants all Electric Assault Rifle allies Increased Hit Rate and Increased Max Ammunition Capacity for 10 seconds.

Place the Electric Assault Rifle DPS in the leftmost slot of the squad.
Auto play is usually enough.
In Arena, if aiming for the 2-second invincibility, set front-row placement and Burst order by hand.

There is only one Burst 2 slot, so she swaps with other Burst 2s like Crown. Outside an Electric Assault Rifle line, she mostly keeps only Peaceful Tree2's lasting max HP and leftmost invincibility.

If Clip Rocket Launcher reloads are frequent, prioritize Resilience Cube. If you need more Burst Gauge, add Quantum Cube. Bastion Cube refills ammo to keep Charge going. If Harmony Cube levels differ a lot, use the higher-level cube before following the ranking.

Elemental Advantage damage and ATK are the baseline. Adjust shots between reloads with Max Ammo to suit Rocket Launcher handling. To shorten the time to Full Burst in Arena, add Charge Speed lines separately.

Peaceful Tree2 funnels attack damage and reload into one Electric Assault Rifle, so raise S2 first. Mother ForestB holds team ATK and Spreading Roots/Withered Roots, so raise Burst next. Nature's Grace1 is Full Burst-end healing and Full Charge emergency healing, so fill it with leftover resources.

Against Wind bosses (Electric has the advantage), matching elements adds damage support. Solo Raid and Union Raid teams using her with Electric Assault Rifle DPS appear. She is also used in Missilis Tower for survival and buff slots. In Arena, she goes in teams that use a Clip Rocket Launcher along with invincibility and ATK buffs.

Grants all Electric Assault Rifle allies a lasting max-HP-only increase.
Grants the leftmost Electric Assault Rifle 2 seconds of invincibility plus increased attack damage and Reload Speed.
Mother ForestB grants all allies ATK, plus an all-enemy Burst Skill damage increase split by enemy count.

The core of Peaceful Tree2 and Mother ForestB depends on Electric Assault Rifles, so without that line her buffs shrink greatly.
Her Burst cooldown is a short 20 seconds, but her own damage contribution depends on Rocket Launcher handling.
Spreading Roots and Withered Roots change with enemy count, so expected value differs between single bosses and mixed mobs.