"What happened?" your mom asks. "It's a long story; you'd better have a seat. I'll be right back; I have to phone you in sick today."
Your mom leaves, and you sit down on the chair. You shoot right up again when you feel a stabbing pain in your backside; your new tail takes some careful positioning to sit comfortably with. Presently, your mom returns and also takes a seat.
"Back when I was your age," she begins, "I was what my mother called a 'wild child.' I didn't really get into serious trouble, but I was irresponsible and thoughtless in a lot of the things I did. One day, a carnival came into town, and my 'friends' and I were walking through the grounds, being a general nuisance. We came to a 'gypsy' tent, and assumed that it was a fake, as most such attractions are. So we went in and made fun of the old woman running the place. When she protested, we started trashing the place. It was mean, probably the worst thing I ever did; all she had was that tent and the attractions inside, and we broke a good number of them. Worse, we pulled out the support pole, and some of the stuff hanging from the ceiling turned out to be a lot heavier than it looked. She was almost seriously injured by falling objects, and we were forcibly ejected from the grounds. She accompanied us to the fence, and she placed a curse on us; at age seventeen, each of our firstborn children would have their life irrevocably altered, losing a year and becoming something other than what they were. Of course, being skeptical teenagers, we laughed it off, and never heard from anyone connected with the carnival again. To make a long story short, I realized that what I had done was wrong, and I reformed. My 'friends' didn't, and we parted ways after that. It wasn't until I had you that I remembered the old woman's curse. Ever since, I've been researching, just in case it should turn out to be real, as it obviously has."
Your ears perk up. "Then did you find out how to reverse this?"
She shakes her head. "What I found out was that unless the original caster wills it, it's absolutely unreversible. Even surgery would be of no avail; you'd gradually change back to the way you are now. And the old woman was close to ninety then, twenty years ago; there's no way she'd still be alive. As far as I know, you're stuck this way for good. All I can say is that I'm terribly sorry, and I want you to know that however you choose to deal with this, you're still my child and I still love you very much."
Your mother's love warms your heart, but you find yourself tearing up anyway. "D-deal?" you say, voice trembling. "I can't d-d-deal with this! I'm not a girl, how am I suppose to pretend to be one?"
Your mother smiles sadly. "That's something else I found out; the details of the curse's effects. You'll grow used to it, though gradually; you won't lose the essence of yourself, but you'll think and feel like you would if you had been a girl all along. It's begun already; note that you were able to put on girl's clothing without your mind objecting, and that you actually knew how to put on a bra. At least you won't have to deal with the stigma of being transsexual, though; the rest of the world, aside from the two of us, remembers you as having always been female, though not a cat-girl. As for that, it's hardly something that will threaten your legal identity, and hopefully those that realize it's not just a costume will take it in stride. You can offer them some explanation if you like; most of the changes you've experienced bear resemblance to actual medical conditions, so a little browsing in a medical textbook should help us put together a sufficiently scientific-sounding string of condition names. Speaking of your legal identity, though, your name's different now. As far as the rest of the world is concerned, your name is Charlotte."
You sit there, stunned. You're stuck as a cat-girl, for the rest of your life, with apparently no hope of changing back. And not only that, but you're going to get used to it, albeit slowly. Even now, the name is clicking in your mind. Charlotte. That's right, my name's Charlotte, isn't it? Well, no it wasn't before, but it is now. I go by "Carlie," though, don't I? Even the fact that you're accepting your new name isn't causing more than a prolonging of your current shocked state.
Your mom is watching you with concern. "Are you going to be alright, dear?" she asks.