With her skill kicking, she deals a fixed amount of bonus damage based on how many enemies show up, and deals bonus damage when she changes targets. The good part is that since it's a fixed amount based on enemy count, the rest of her stats don't matter. Doubly so because it ignores Armor, Evasion, Shields, etc., so she can still be useful while suffering from the stat penalties of using Parachute Fairy.

She has very weird mechanics. I want to say something witty but that's really how it works. The most immediately noticeable thing is that her damage is actually cut in half and she fires twice. This seems odd but no, its not just a visual thing either, and both shots actually can end up on different targets. The first shot uses normal RF targeting, while the other has real time targeting to always shoot the farthest target. Vs heavily armoured (enough that AP rounds wont go all the way through) or high HP enemies, this can be bad. Or it can be excellent at trash clear.

Also note that because she shoots twice, it only takes half as many firing cycles as it says on the skill to get stacks, as she gets 2 stacks per cycle (1 per shot). It also has interactions with Sei and Jill that are in the detailed page.