I can't answer with a properly medical reply, but certainly if she has constant diahorrea, that means she's not keeping food in, and can call weight loss. I'm glad for her that it's being treated as an urgent case, any changes in bowel habits should be investigated. May I suggest that neither of you speculate what it might be? - you will know soon enough, and going on the internet can be very scary indeed, You need facts at this stage, not worst case scenarios. Good luck to your daughter for Tuesday.