You didn't mention the brand of food you're giving her. Is it a premium food or supermarket stuff?

I'd switch to a premium diet, like Hills or Iams. You might also want to try giving her a little canned food each day, again use Hills or Iams.

If the vomiting persists, try a sensitive stomach formula, hairball formula or the lamb/rice formula.

I would also start her on Laxatone or Petromalt or another brand of hairball remedy on a regular basis. These are usually pretty palatable to cats and can be given as a treat.