Purina is ok but it is not very good quality. Poor quality food is like feeding a kid McDonalds everyday. If you can, it would be a good idea to switch her over to a food that comes from a pet store like Petsmart. There are all kinds and you can do a search on these forums for posts about quality food. There is Nutro, Chicken Soup for the Cat Lovers Soul, Innova, Solid Gold, and lots more.
The point is you want the majority of the first ingredients to be meat and not corn or by-products. By-products are bad. You can try wet canned food too but the same rules apply. All these brands have wet food too.
You may spend more up front on these brands. But it will keep her healthy and cut back on vet visits. Also it will fill her with quality ingredients faster and she will eat less at each meal time and it will keep her fill longer. Whereas the cheap foods fill her with fat and fillers and bad ingredients and wear off faster so she will be looking for food sooner.
Sorry for the lecture.