If someone commits assault and the victim doesn't want to press charges, can someone else do it?

This guy my daughter has been hanging out with beat her up and threatened to kill her. She's scared and refuses to speak to the police because she thinks it's going to make everything worse. Possibly because he has connections with a bad group of people. There seems to be no way she will even consider pressing charges. I know for a fact that he has been arrested before, but I don't know for what. She won't take a picture to show proof that she was beaten, but she has bloody clothing that I'm hoping can prove something. Is there anything I can do by myself to see to it that he goes to jail for this? And how long would I have to report it - Is there a limit before it becomes to late too do anything at all?