Ah, the gay awakening!
Well, I guess Akira's always liked girls but comphet's gotta comphet?
Edit after rereading: She did always like Rumi a bit more than what you'd expect for a best friend, and there was a whole thing about thinking whether her being a girl would make her like boys or not, back when they got Sex Ed, and she always had trouble talking about her type of guy.
I guess she never considered homosexuality as an option until now because she never had any exposure to it, even if she was told it was a thing.