I haven't noticed this happen for me. My feet are about a 12W or a 13 in Women's shoes. Though, if I go in men's, I could usually get an 11W or a 12 without much problems.
Shoe shopping is mostly a pain for me, so what I usually do is just get a nice pair of neutral looking sneakers from men's.
I am tall for a woman at an even 6', so heels are just something I don't do. Though I have gotten some nice flats and some feminine sandals at Payless.
I am sure there is something out there for you. Even if you just get one pair of heels or some flats for a special occassion. I think most women who wear heels all the time just end up getting back problems and that sort of thing which is also another reason I just don't bother with heels!
My thoughts are that as long as you're practicing things like having a feminine walk, mannerisms, and just an overall feminine essence, the shoes you wear or your foot size shouldn't be a big deal in regards to passing as a female.