What Causes Mood Swings And Unhappiness In An Adolescent?

I have a eighteen year old daughter. Her mom and I went through a divorce when she was eight. Since then she did not want me to hug her or get to close to her. It still is that way with her mom and me and her moms husband. She seems to be happy most of the time but her mood can change quickly. She pretty much stays her room when she is with me or her mom. She has lots of friends and a boyfriend and seems to be happy when she is with them. We can have good conversations. When I asked her if she feels angry at her mom and me for the divorce she says no. But I still can t help thinking that there is some deep rooted hurt or something unresolved in her because of the divorce. I don t know if this provides enough info. What do you think