I am sorry to hear that. Maybe take baby steps and get her to just lightly touch the area near your anus while giving you a BJ or HJ. (The area between your anus and balls) Or have her try it during intercourse.
Next get her to just touch your anus and lightly rub it with a oily finger.
ES
Actually, she does all of this and it drives me crazy. I have begged her to push on inside of me and she refuses. She thinks it is nasty.
It is kind of crazy because she is a sexual dynamo. This is her only no go, giving or receiving.