In all likelihood, she was exposed to some kind of abuse before she was put up for adoption (unless you adopted her as a newborn?). And even if she was adopted as a baby, as she becomes old enough to comprehend that her birth family "gave her away" she will have issues to deal with.
Because both our children were adopted my husband and I have read a lot of the books and stories that explain how it feels to be an adopted child. All of them eventually have to deal with this basic anger/insecurity. They ask "why didn't they want me?" Sometimes they will react with violence against those who love them, and it may be that in doing so your daughter is asking you to prove that you will love her "no matter what". That "no matter what" expresses a fear that is at the heart of each adopted child's psyche. They were "discarded" once; what is to say that you won't do the same? So they behave badly because if they are going to lose you they want to get it over with. Their anger is fueled by terror.
I'd really recommend that you 1. read some books written by others who have gone through what you and your daughter are going through (do some research on a rated system like Amazon to find books that others found helpful, be sure to read the reviews to find out why they liked it), and 2. find a good counselor. The physical attacks need to be addresses immediately and you may need some support in order to deal with them in a positive and effective way.
Getting back to the subject of abuse (and forgive me if you adopted her as a newborn so this isn't relevant), one thing I know from living through an abusive childhood and spending several years as a counselor for adults from abusive homes, is that all abused children have a huge well of anger in them. It doesn't matter what kind of abuse it was; the anger seems to be a constant. And the degree of anger doesn't necessarily depend on the level of abuse. Different people are more or less disposed to anger. I've had years of therapy and I openly tell people I'd be a terrible human being today if I hadn't had good counseling. Abused children don't have a roadmap which will take them to good destinations. The places theirs take them to are places you don't want your children to end up in. They need to be given a new map and guided down that better path.