Personally, I don't think it matters - although you want to make sure she has a good appetite before giving a shot in the beginning when you don't know what her response will be.
Both of my guys would eat almost anytime/anywhere except the few occasions that Beau had a p-titis episode. He always ate less and less over about 48 hrs, so I knew to reduce the dose a bit, based on his numbers. With him I fed, then tested and shot about 15 mins later. I free feed all my cats, so with Jeddie I don't even have his shot timed to him eating.