Because she wasn't attracted to you as a boy

"... because you never turned me on this much before."

"Before? Before what?" you ask, but on some level you feel with a sense of dread that you already know exactly what she's saying. "You mean before, as in ... you aren't attracted to ... the real me." She doesn't say anything in response, but that already tells you all you need to know. You fall back into the couch in shock. Your mind is just running in circles, but somehow your mouth manages to keep asking questions. "So are you a lesbian, then?"

"I don't know. I've never really felt so strongly attracted to anyone before. I always just assumed that what I felt was normal. I mean, I could tell that you were handsome, and I knew that was what I was supposed to want, so I just sort of went along with it. But lately I've been noticing things, like how tight those little shorts Lyla always wears are, or Michelle's endless cleavage, and... I just... I just don't know. And earlier, when you kissed me, I got really wet. Like, I didn't even know I could get that wet."

She trails off, and after that, the room is silent for a while. Then your brain starts to catch up with the conversation, and it suddenly hits you where all of this is going.

"You're breaking up with me?!" you shout, loudly and angrily, while leaping to your feet. You stand looking down at your girlfriend, or ex-girlfriend now, with hate burning in your eyes. "With everything I'm going through right now, you still thought it was a good time to just dump me like it was nothing! Like we were nothing! I can't believe I ever even liked you, you selfish, heartless bitch!"

... Rather, all of that is how you would have reacted just yesterday. Instead you barely make it through the question before you break down into a pathetic mess of uncontrollable sobbing, pulling your arms and legs up into a fetal position. Stupid fucking estrogen. Allison comes over and pulls you into a hug, and you can't fight it at all. You cry so much into her shoulder that her top must be soaked through. As you start to come down she rocks you softly back and forth, running a hand slowly through your long hair. You like that. "I never wanted to hurt you like this, John" she seems to have trouble forcing the name out "I just... looking at you... you look so beautiful, I couldn't hold it back anymore". She pulls back from the hug and looks into your eyes, with a look you've never seen on her face before. It looks... right. Beautiful. Caring.

It looks like love.