Gosh...finding one with her diaper is super rare. She is relatively hard to find, harder to find with her fabric diaper and seldom comes up with her painted one still in place.
If you were selling I would recommend you auction her as you will get lots of interest. If you prefer a trade value on her then honestly thats tough as she seldom comes up and even though she is the most common of the set, I would still say $100-120 for her.