As a Hull University Alumni, I must admit this is very sad news to hear.
If you look at where she went missing, there's the tributary for The River Hull and the River Hull itself not far away. Granted I'm not sure how the poor lass ended up there after she got back from The Welly, but if she was wandering in the dark and fell in, cold water shock might have got her before anything else.
It's her parents and friends I feel for.
I hope it was an accident, but the circumstances surrounding it are so strange it makes me suspect foul play.