if she ate fast and threw up immediately after (and it came out pretty much as it went in), it could have been a scarf & barf. They eat too fast and it comes right back up. Most of the time, if you try to feed again in 20-30 minutes, they'll eat again if that's all it was.. just keep trying to give her small meals ...a teaspoon at a time for awhile and see if you can get some food into her after her stomach has a little time to settle.
Since you said she also threw up a hairball, she could still have an upset tummy too. Nobody wants to eat when they don't feel good.
Do you have any Pepcid AC? 1/4 of a 10mg tablet can settle their stomachs. If you don't have it, next time you go shopping for supplies, you should try to get some (generic from WalMart is fine) It's one of those things you need to add to your "just in case" case
Since she's going insulin on board, if you can't get any food down her, you might need to syringe feed if she doesn't agree to eat a little...or a trip to the vet to make sure there's nothing more serious going on.