Cat's shouldn't eat dog food.
A cat's nutritional requirements are much different than those of a dog. For example, cats require higher levels of protein than dogs. Cats must have the amino acid called 'taurine' in their diet; dogs can actually make their own taurine. A cat eating food deficient in taurine can develop severe heart disease and other health problems. Almost all cat foods now contain added taurine.
So, you see, if a cat is allowed to eat a significant amount of dog food, the cat would be eating a diet deficient in many of the cat's required nutrients. For your cat's health, be sure she is eating quality cat food.
Hope this helped