Your vet will definitely be able to answer this question. But in general the kind of anesthesia that is usually injected is a ketamine cocktail, which inhibits vomiting. So it's not a huge necessity to fast the cat but they still shouldn't eat a huge meal.
If you don't get an answer from the vet, what you can do is pick up all her food before you go to bed tonight and then give her just wet food in the morning. This digests quickly so it's not likely to cause problems. Plus it's better for her not to have a full stomach so she doesn't vomit in the car on the way to the vet!