What your W is telling you could very well be the truth. Women come in different sizes...just as men do, she could be someone who is smaller on the inside (which doesn't necessarily mean she'll stretch over time). Also, there could be a lubrication issue which causes chafing for her (and man that can be irritating!!) If you don't use lubrication, try some astroglide.
Also, obviously I don't know how fully you penetrate her...but you might try not going as deep as you usually do to see if that makes a difference too.
Just some thoughts. If she truly does experience discomfort...then have you discussed alternatives that she can do for you? Is she open to that?
