Corn snake growth and feeding?

I would stick to mouse pinkies. If she is 20 inches long, I would give her at least two pinkies. I feed my corn snake 3-4 pinkies at a time, every 5 days and he is getting close to 3 feet long. She will grow faster the more you feed her. Temperature plays a big role in digestion also. If your corn snake has the ability to reach a belly temperature around 90 degrees F. They can fully digest a meal in 2-3 days. Hope this helps.