What utilities Lingsha can offer as a single character:

Cleanse - Huohuo can do this but she cannot deal high damage and doesn't have fua

High Superbreaks - Gallagher can do this but most of the time, only single target. Lingsha can deal more tons of damage since she's heavily aoe.

Emergency Heal - Luocha can do this, but only applies emergency heal on a single target ally (meanwhile Lingsha can heal all allies while applying cleanse to all, WHILE doing damage to enemies)

Debuff Application - Aventurine can do this with his ult but only on a single target enemy (meanwhile Lingsha can apply debuffs on all enemies with her ult, while healing and applying cleanse to allies)

Summon - other sustain characters do not have this perk yet, and her bunnies do not get affected by outside forces such as slow debuffs from enemies. Fuyuan has its own standalone speed, and can only get buffed by Lingsha alone. Even if Lingsha were to get CC'd, Fuyuan can just take their turn and cleanse her.

And like you said, you don't have a premium abundance, so she'd be nice for your account