I am so sorry your girl is not feeling well.
If she eats dry food that may be the culprit. PLEASE READ:
Cats do not have whims like people. Anytime they refuse food, they are sick or in pain.
The first thing I would suspect is an abscessed tooth or root in her gum or a sore or stuck item.
Check inside her mouth for any abnormalities.
Lack of fluid in the bowel also leads to vomiting, Ingested hair can also be a factor.Anorexia for any extended time leads to liver damage and causes nausea and vomiting as well.
I would add some canned or baby food for her
Serve the two foods separately - do not mix them - add a half pepsid a/c tablet, crushed up into the wet food one time a day.
Cats are attracted to smelly foods - the stronger the better. If she wants tuna, give it to her You can also try fancy feast, clam juice or baby food.
human baby food in meat flavours (check that there are no onions or garlic in the ingredients) and mix that with warm water and offer that, or syringe it in little bits into your cat's mouth. Beech Nut makes a line of baby food that has nothing but meat (beef, chicken, turkey or veal) in it. Here's a link: http://www.beechnut.com/Our%20Baby%20Food/Results.asp If you cannot find this, you could find another meat baby food - just read the label carefully to be sure there are no onions, onion powder, garlic, or garlic powder in it.
If her tummy needs a rest, feed baby food with no onion or garlic for a few days.
If she wont eat, and your cat is not diabetic begin by giving her two droppers (cc size) of unflavored pedialyte every ten minutes for an hour. Next water down(plain water) canned cat food or baby food chicken or turkey with no onion or garlic and give only one dropper every ten minutes for another hour. Wait two hours and repeat both. When she feels hydrated she will lick up the gruel on her own.
Give her droppers of unflavored pedialyte a few times a day to make sure she stays hydrated.
If she throws it up have her seen immediately!
Please let me know how she is doing. I will always be here for you.
I hope she feels better very soon.
Sincerest best wishes,