Leila is an evasion tank with a Lock aura. She wants to open with her EX to inflict her Dazzle debuff on the enemies. You want to maintain her buffs otherwise. Leila is very hard to kill herself and also helps the party survive aoe attacks through the boss missing or simply mitigating any damage that does manage to get through.
Thunder XVI is an AoE brv shave that grants her Big Sisterly Boss buff. This provides stat boosts to the party.
Provocator's Edge grants Leila her overhead buff, Swashbuckling. This overhead increases Leila’s stats and HP damage and increases her evasion to 100% while reducing the party’s HP damage taken. This also is an aura taunt, forcing enemies to attack Leila and giving her Last Stand to survive guaranteed hits.
Leila’s EX is Lightning Turn. This is a fast charging EX, requiring 2 skill uses to refresh. This inflicts Dazzle on all targets, inflicting Thunder Resist Down, reducing their BRV Damage dealt, and lowering their hit rate.
Detonator is Leila’s LD, granting Leila her Stormsurge buff. This buff raises the party’s BRV and HP damage dealt, grants them HP regen and batteries the party by their damage dealt. This also allows Leila to "counter" the enemy whenever she evades an attack. This counter heals and batterys the party before moving Leila’s turn to the immediate spot followed by ally turns. These turns also all count as free turns and will not add to the turn count.