Men may find it hard to believe, but there are ladies who just can't believe that their boyfriends are actually enjoying themselves "down there". She is going to take some convincing. I guess you could try getting her to ask her friends if they are into oral sex. Try getting her to join Pixies (although communicating with us randy old perverts might blow her fuse).

A tip: lie her on her back and tell her to keep her knees together. Then kiss her all over. When you eventually get to the most interesting bit you should still be able to slip your tongue far enough into her furrow to play a symphony on her clit. She might accept this as a compromise, and if she does, one day those knees are going to ease apart....