When Lemmie CFRs you, I take that as her way of telling you the facts probably don't back up your opinion (especially in the case of sexual development in children). There are a lot of really smart posters here that are much better versed in childhood development than me (paging Jersey Girl) and I hope they will take the time to show you where you are off-base.
That said here are some good jumping off points for you in learning how a 12 year old could think she is attracted to the same sex.
From the American Academy of Pediatrics, a wonderful paper on orientation in adolescents.
Because self-awareness of sexual orientation commonly occurs during adolescence, the pediatrician should be available to youth who are struggling with sexual orientation issues and support a healthy passage through the special challenges of the adolescent years.
And here, a chart with development milestones with some excerpts relevant to the conversation. (PDF warning).
10-12 year: games with peeing, sexual activity (e.g., strip poker, truth/dare, boy-girl relationships, flirting, some kissing, stroking/rubbing, re-enacting intercourse with clothes on)
Young (12 – 14): psychologically distance self from parents; identify with peer group; social status largely
related to group membership; social acceptance depends on conformity to observable traits or roles; need to be
independent from all adults; ambivalent about sexual relationships, sexual behavior is exploratory
ETA: Thank you, Jersey Girl. I figured you would probably want to jump in on this one.