Vomiting on birth control?

I've never had this problem, but my mom did when she was younger and on the pill. She'd wake up in the middle of the night and throw up. I don't think it ever went away for her. Your best bet would be for her to go back to the doctors. There are pills with different levels of hormones, as well as the depo shot (that doesn't contain estrogen if that's what she's allergic to) which are alternatives. Good luck, I hope she finds something that works for her.