My cat has a vomiting issue from time to time.
I'm not usually too concerned about it, as long as it doesn't last for longer than a couple of days. If this has been going on for some time, I'd be tempted to take her into the vet to see what they made of it.
At one point I had to give my cat ear drops, and I have several scars to prove it!
Edit: Or just do what badaboom said.