So do I understand correctly you are a witness to the crying, not the party? Does the crying wake you up - or does "she"wake you up as tell you she was crying?
Crying must be related to dreams, unless she is actually crying because of something on her conscious mind. Try to help her understand why she is crying regardless wake or asleep. Dream problems can be resolved. I think it is a general truth that bad dreams are the result of our minds, the one we use when awake, is trying to resolve something. If you can identify what that is and resolve it when awake I'll bet the dreams (assumed in my input) stop.