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.

Yes, Pekola, as opposed to a certain dumb rabbit. The eternally-starving once-most-powerful angel. She actually won't attack at all until you meet her conditions of getting enough buffs. Thankfully, stuff like Python's FP buff stacks count as individual buffs. More hilariously, the fairy talent Fervor also counts as three buffs. This makes satisfying the conditions for her skill actually pretty easy.

What you get for doing so is a ridiculous RF that completely ignores enemy armor and shields. A major downside to this though is she wont deal as much damage as another RF if you don't need such capabilities, since she isn't affected by very many damage buffs due to how she works.

This should be obvious, but you should pick up her unique gear if you plan on using her.