I guess this is a bit different, but DD went through a phase of waking up in the night and coming in to us because 'I can't get back to sleep'. We couldn't work out any particular reason for it, so in the end we did her a star chart, which we stuck on the outside of our bedroom door, so she saw it when she was on her way in to wake us up. We did, of course, say that if she was feeling ill or anything, she could come in and wake us up. I'm not sure this would work with your DD though, as it's more difficult if she's upset about things. It did work for us, after a week or 2. Maybe worth a try?