Yeah, this looks almost exactly like nurse akali's. It'll be hard though to make a different looking skin when they're both under that title of "nurse."
Overall, nice drawing, but it doesnt really look like katarina. Definitely might wanna think of the scapel idea instead of knives in the position of syringes. And she has to have flatter, straighter hair. I agree with other posters when they say the hat make her look kinda like MF--I think the hair is also making her look like so.
With a bit more fixes here and there, I could see myself purchasing a skin like this for kat.