Despite Sofi's frantic motions for you to turn back, you head inside. You want to get this whole stupid thing over with as quickly as possible, and this sounds like the best way to do it. Sofi's mother welcomes you in and motions you to a seat. "So," she says, "assuming I haven't decided to take advantage of your stupidity and just hex you on the spot, what is it you want to talk about?"
"Well," you say, "I talked to your husband, and he said you'd unhex me if I provided a replacement cursed ride. Your daughter suggested that I could make one by using your spelbooks, and so I was going to ask if I could borrow them."
She grins a broad, unsettling grin, and you begin to wonder if maybe you should've listened to Sofi. "So," she says, "you want to use my spells to make another cursed ride so you can leave the carnival, right?"
You nod, glancing sidelong at the door. "Well," she cackles, "I think you missed the point. I'm not angry because that was an important attraction, I'm angry because you broke one of my curses. So I'm not in the mood to give you what you want right now. Still, my husband did promise, and I think I see a way to release the both of us from this agreement without giving you the satisfaction of winning." She makes arcane gestures, and you see a shooting gallery with all kinds of seemingly inocuous prizes appear outside the window. Then she stares deep into your eyes and mutters cryptic words of power.
Suddenly your skin feels like it's on fire. You leap to your feet, only to discover that you're shrinking, and watch in shock as orange tabby fur sprouts all over your body, except for a patch of downy white that runs from underneath your chin down to your groin. "What's happening to me!?" you shriek, your voice jumping up a couple octaves.
Sofi's mother chuckles. "Well," she says, "I'm just doing things my way, that's all."
As she's speaking, you watch the front of your face push out into something in between a human face and a cat's muzzle. You feel your ears change, moving to the top of your head and becoming thin and triangular, and long silky white hair spills down around them. You watch pads form on your palms and see your fingernails become retractable claws, and you can feel your feet becoming full-fledged cats' paws.
By this time, you've shrunk to no more than four feet tall, and your now-oversized pants and boxers have fallen off, leaving you clad only in a tee-shirt, which fortunately covers up everything that needs covering. As a tail bursts forth from the bottom of your spine, you feel a sucking sensation as your genitals are drawn up inside your body. Then the changes are finished, and you observe what you've become: a young cat-girl of about twelve years old.
"There we are!" the witch beams. "You're free to leave the carnival now, but you probably won't have much to go back to, having no legal identity and all. So you might as well stay here; you'd fit in wonderfully in the freak show, or you could work behind the scenes at one of the other attractions. It's up to you!"
You dash out of the trailer before she can do anything else to you. "Toldja it was a bad idea," Sofi says. "Still, it'll be nice to have someone my age around."