Welcome to Healing Well. I'm sorry to hear your wife was having such a tough time. Has she been able to relieve her migraine yet?
Another solution, rather than the ER might be to go to your family doctor to get a prescription. Sometimes ER doctors won't prescribe the needed medications because they believe headache patients are drug seeking. Your wife's headache doctor might be more likely to give her the correct medication at the strength that she needs.
I agree with Annuk, the best person to see in the long run is a headache specialist, a neurologist who specializes in headaches. S/he can prescribe preventative medications and provide your wife with the necessary medications to relieve her migraines when they get out of hand.
I hope that you both find some relief. Bless you for being such a kind husband. I am lucky to have one just as kind, and I know how nice it is to have someone to help when you feel like you are dying.