Interesting. I find that my need to crossdress disappears when I'm in a relationship, so it never becomes an issue. This is perhaps due to the fact that my crossdressing is such a tiny part of who I am and that because my attention is focused on my relationship, Andrea effectively gets the ax.
I've never had any doubt as to my sexual orientation, but you raise an excellent point vis-a-vis the woman's point of view in a relationship in which the man is actively corssdressing or wishes to crossdress openly. I suppose in these scenarios it is on the one had competing with the "other woman" or raising questions about sexual fantasies that challenge one's notion of "straight" and "homosexual."