No, you can't say "my character is a good person, so this is okay." But you can say "my character is a good person, so she thinks it justifies the means." That is the slippery slope you are following. It can lead to your character becoming more and more an evil person. Or she can become jaded and cold, knowlingly sacrificing anything in the alter of the greater good, even her own soul. Or she can become more and more deluded, thinking the powers she uses are good and she is doing good things.
Naturally, it doesn't matter why she is killing, transforming, mindraping or enslaving people - it is still an act of imposing her will forcibly upon another with magic, and that is what makes it Lawbreaking. It also doesn't matter why she is violating life, time or the borders of the universe. Those are still acts of her imposing her will against the will of whoever made the universe as is, and thus by extention an act of imposing her will on everyone within reality - and that is what makes it Lawbreaking. In the end, Lawbreaking is the act of imposing your will against the free will of another in a permanent and irrevocable manner.