Concerned Mother of Teenage Daughter

My daughter is usually a very warm and empathetic person. She's always putting people's needs ahead of hers and is generally easy going. Sometimes, however, it seems like a switch is randomly turned on and she becomes the exact opposite - she becomes cold and distant and very unsympathetic to other people's feelings. She hasn't had the easiest childhood so far, is there a possibility that her aggressions could possibly be her way of dealing with it or her unintentionally imitating the behavior she used to grow up around? I want to help her through this, but I'm truly at a loss here.

How old is your daughter?