Why did i have a nosebleed, feel dizzy nauseous and vomiting?

Okay So my Gf was crying for about ten minutes. then out of nowhere she had a nosebleed. it was bad but not too bad. she was snotting up and hacking up bloody mucus and stuff. Then after her nose stopped bleeding she started to feel dizzy and then sick to her stomach. then vomiting. Shes On her period shes been having heavy normal flow for the past 3-5 days. we have not had any adult like contact for over a week. So she is not prego. She usually has nosebleeds every so often. She also just started taking birth control like 4 days ago, the pill. She has told my shes had pain in her abdomen and a warning sign on the BC list she got was go to the nearest emergency room if she had pain in her abdomen. But please mature answers and stay on the topic thank you all.