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.