Sleep-Showering?

Last night as Marc and I sat in the living room chatting with friends we heard the shower turn on. As I went to investigate, I found our 9 1/2 year old taking a shower. Mind you, it was 10 p.m. and she had been in bed since 8:45. Is it safe to assume she was sleep-showering? When I asked her what she was doing she said, "I don't know. I don't know why I'm taking a shower." I can only guess she did wake up when the water hit her! :-)