What Does It Mean If Somebody You Know Cries In Their Sleep?

Somebody I know cries in their sleep around the same time every night. It's like somebody turns up the volume nob because at first it will be very faint and then it gets so loud that it can actually wake you up. But, in the morning she doesn't remember it. Is their something a matter with her or is it normal for a 6 year old to cry in their sleep? Some facts about her crying: It is around 10:30 PM every night Her parents got divorced a year ago She demands the most attention