Ideas needed for what my character can do?

your right those characteristics would make her a bit of a cliche. How about dropping the super ninja thing and giving her more of a dark mental ability? something like being able to reach into someones mind and pull out there deepest, darkest, most paralyzing fear and multiplying it ten times over. For example if you have a fear of spiders you will suddenly find yourself covered in them. (you can either make it real or illusion that is up to you.) emotional stress such as fear or anger makes her power harder to control. If you want to stick with the idea of her as a martial artist then maybe she took it up as a way to discipline herself in order to better control her emotions.