I agree i dont think it sounds like abuse....i think shes being a typical 2 year old, she may have a diaper rash
and doesnt want you to make it sting, i know when my son has a diaper rash he sure as heck doesnt want me wiping him, he squirms and yells at me and everything else. i think thats all it is.........i dont know if shes old enough to relate the two. im not sure though, i would be concerned too. i would just keep my eye on the situation.