I was beaten on the subway. The girl ran away. I reported the case to the police. They said they’d find her. What specialty of a lawyer should I look?

I'm not sure why you think you need a lawyer, at least before the person who assaulted you has been located, but if that person is located and you want to sue her, you should contact a personal injury attorney.  Personal injury law is a branch of civil litigation.  There is no reason why you should need a criminal attorney if you were just the victim of a crime and are not being charged with one.