Well I definitely think it is something in the water. My DS 26 months, has been waking up every morning at about 2-3am and crawling into our bed.

My DH tries to pick him up and carry him to bed but he wakes up and screams go way daddy and will only go to sleep when I lay next to him and I have to make sure he is totally passed out before I leave or he will just end up in our bed again. We just can't have him in our bed anymore as DS2 usually is in our bed as we co-sleep with him as he gets a bit of an upset tummy.

Maybe DD is overtired and she finds it hard to get back to sleep? I know the more tired my DS is before bed the longer it takes to get him to sleep and he seems not to sleep so well.

Do you think DD could be getting more teeth or is uncomfortable with the rash and that is unsettling her.
Sorry that I haven't been able to help. Fingers crossed you can find something to help soothe your lil one. I will be sure to post if we find a breakthrough!