Maybe there is another problem that you are not aware of. Did someone hurt her in some way or another.
The other side: It is hard, but remember, that our kids use us as role model. They see what we do, how we react and what we say. I made the same mistake and learned from it.
Talk to her. Set some ground rules and tell her that you do it because you love her. If you leave it now, you really are going to feel like running away when she hit teenager.
Good luck