My girl needs help eating.

Hello, my girl has plenty of problems from menstral cramps that are so painful she passes out and needs strong pain killers to help, doctors are still working on the cause, but it seems genetic, all girls in her family seem to have a their own degrees of pain and cramps.

But she has created her own problem on top of the normal problems she has had for a long time. She stopped eating an when ever she did she vomited it up in secret.  Now when she eat, her body will cramp painfully really bad and wants to vomit.

She needs to eat again like normal. I figured she messed up her body so when she eats it cramps and tries to vomit, sense she use to do that so the body got use to doing it.  I figured we can work up from liquids to yogurt to solids. But idk if that will work.  

Trying to take her to the Doctor for it is impossible I will have to knock her out or drag her kicking and screaming. I think shes more ashamed that she caused her own problem.

So i been trying to get her to work her up to eating.

Any idea or even some over the counter meds that we can use so her stomach won't cramp with severe pain?