In some ways this might be considered a healthier reaction than punching other things. It shows that she is trying to control herself, but she doesn't know how.
My son had anger issues and it helped when we got him one of those inflatable punching buddies. We made sure he understood that it was absolutely okay for him to punch it as much and as hard as he wanted. When he popped it we just bought him another. I think it helped that we were able to explain to him that there is nothing wrong with feeling anger. The important thing is what you do when you are feeling that anger. There are "good" ways to express anger, and "bad" ways. Give your daughter good ways and she won't need the bad ways.
Some children feel the need to express their anger physically, with punching or destruction, and others can express it more cerebrally. My sister used to give her daughter reams of paper and tell her to draw pictures of how she felt when she was angry. This resulted in many pictures of my niece hitting or shooting people, of my nephews being hanged, decapitated and thrown into sewers, and once of several pieces of paper being cut up into tiny pieces and thrown all over her room :)