If she had done stomething like allowed you guys to bring in cell phones when you wern't allowed (this is just a hypothetical example) and you got her fired for that, then yes that'd be wrong of you (in my book).

However she was clearly violating the law, and doing things that were morally and ethically wrong for her position. You did the right thing and can't let yourself get upset over it. You feel bad about it so it's already evident you are a good person, you did the right (good) thing by stopping someone from doing something blatantly wrong.