I played a pure female V for my first run through. I went out of my way to flirt with Panam only for the romance options to just kinda of disappear. I really thought Panam would've been a possible romance option for me and I was really disappointed that it wasn't actually possible despite the hints and no outright refusal (from Panam).
Heck, even if you go flirty from the starting line, she clearly warms up to you with her own flirtations since she has her own issues that need sorting out before she's ready.
I know I could go with Judy, but she's just not quite my type. A good friend to have, no doubt. Just not my type for romance.
EDIT:
Since a few people seem to not be reading the thread, I'm going to quote myself here.
I simply felt strung along by Panam, based on the choices I made and never encountered a clear refusal. That's why I felt Panam was bisexual even if she was not designed or intended to be.