I'd agree that maybe she just hasn't had a guy with a big cock who knew how to use it! Some guys with a big dick think that's all they need to please a woman and try and ram it straight in there before she's ready and that's guaranteed to put her off.
I think most women who have had a well hung guy who took his time to start with would agree that bigger is better. My ideal cock is about 9" - I have had bigger and it was great but takes a while to manage it all. 9" esp if it's thick too stretches me nicely, doesn't take me long to take it all and is enough to make me feel full xx