You are not being stupid, you are being concerned by an obvious change in your cat's normal behavior. Good for you. That is usually the first sign that something is wrong in cats. In this case, however, I don't think anything is wrong.
It may be that your cat feels so much better since you fixed her diarrhea problem and put her on a more acceptable food that you are now seeing the true her. It may also be that she sees you as companion and security and she is just showing her affection.
One caveat, if her "affection" tends to cycle like every 3-4 weeks, or she shows other signs of being in heat, she will need to be seen to make sure she doesn't have a piece of ovary left from her spay surgery that might be producing hormone. This however, is very rare.
Yours is a nice question to answer. Sounds like you just have a cat that loves you.
Hope this helps. If so please click so that we can be here to answer more questions like yours. Thank you.