If she is sick ALL the time, there is a possibility she has hyperemesis gravidarum. IF that is the case (and I really hope it isn't, for her sake) she will eventually end up off sick. It's really important for her to talk to her doctor. Unfortunately, they know very little about it BUT it should go into her records. I think some anti sickness medication is OK and safe in pregnancy. The only thing that REALLY helped my DD was Vitimin B6 (given to her overseas) but they don't allow that to be taken here.
Things that helped my daughter. Ice. She would suck ice most of the time. It seemed that the cold helped to calm her stomach a little and helped her to retain some of the fluid. At times, lemon flavoured water (as in, a piece of lemon, NOT a bought drink).
I agree with Hetty. Not putting off vomiting for as long as she can. Although my daughter vomited 7 or 8 times daily, she felt a bit better immediately after vomiting and would for a short window of time be able to eat. Most of it would come up again, but some nutrition would be gained.