I just realized the speculation doesn't really help. What you need to do is talk with your daughter when she isn't angry and upset. I know this is easier said than done and a bit tricky. How to talk with your child and get them to open up is a long discussion and varies child to child. I carry on a lot of these conversations when I'm driving my son places in the car, or going for a walk. The idea that he doesn't have to LOOK me in the face or across a table.

Good Luck.