The best thing to do is take her to a vet for an exam. That is really the best way to find out what is going on with your cat. Occasional vomiting is normal for a cat ..i.e. hairball, eating too much or too fast but if your cat is vomiting a lot there is something else going on with her and she needs medical attention asap. The longer you wait the harder it is going to be to treat your cat.