If she eats fast, that can contribute to the whole problem. Feed her small but more frequent meals. You can also put golf balls in the food dish as an obstacle to slow her down. Make sure you use objects like golf balls. You don't want to use anything smaller that she can swallow.
This a great technique that helps fast eaters.
If she still continues to vomit, then you will need to address her food.
The number 1 reason for cats that vomit chronically are ingredients of corn, wheat, gluten, and by-products. These are hard to digest ingredients for many cats and are unfortunately the most common ingredients in many cat foods. These are ingredients that are not apart of any cats natural diet in nature.
I think if you truly look for natural foods, that will help resolve this problem. You need to find foods that do not contain these ingredients. Do not just go on what the bag says on the front either. Many cat foods say "all natural or Organic", but they really aren't. They just raise the price of the food and put it in a prettier bag so you will buy it.
Here are some foods I think you cat could really benefit:
California Naturals, Wellness, Chicken Soup, and Eagle Pack Holistic.
You can find all these foods here:
Also start feeding him a tsp a day of plain yogurt a day. Yogurt is loaded with good bacteria that helps aid in healthy digestive health. Just make sure you use pain. The fruit varieties contain too much sugar.
I think after 2 weeks you will be pleasantly surprised with the result.