Mountain Lily looks like a Tanker, she got big hp and def bonus. Her speed is mediocre, about 455. Her skill needs upgrades, since 15% trigger rate is shit. So expect to farm the event items to buy skill upgrades, so she can reach 30% chance to use skill.

Don't worry unlike Aigis rainbow spirit, FKG 'rainbow spirit' gives 100% Skill up/equipment slot up.

Personally I'm gonna aim for minimum 5/5 skill up with 3/4 equipment slots. I only have 2 good pierce types.