If u take her to hosptal they will give i.v that happened to me and it eas dehydration
The yellow liquid is stomach bile. She needs to try spreading out her meals and keep something in her stomach, as well as drink drink DRINK lots of water as shes probably dehydrated. I was exactly where shes at now and I still have a constant headache, but its more tolerable now.
When I threw up like that I heard it was acid and she can always take Tylenol that will probably be what they recommend but they might also see her.
The yellow liquid is probably stomach acid. I would say call the doctor, because she could be dehydrated. Headaches can come from dehydration as well.
get her to the docs or call midwife as she cud be dehydrated an they say headache shud only last two hours if longer call midwife