The biggest issue I'm seeing right now in regards to this is Petey. Even if you say you're only interested in girls, your first crush is always male, and he is forced to be your first sexual experience with several of the "first real relationship" choices. And some of those don't even make sense. If I want my first real relationship to be Ava, why do I have to "keep up appearances" and "date" Petey?
There's also a lot of little things throughout the prologue implying an interest in guys no matter what your choices have been. It just seems like this game really doesn't want you to be a lesbian.
Edit: And now that "implication" has gone too far. Despite showing no interest in men, I apparently ended up "filled with jizz" and had to think about going back on birth control. If the game isn't going to let you be a lesbian, then don't make it an option at the beginning.