A great white light beamed out from Margaret's raised arms and surged directly into Kat's body, knocking her backwards and blasting the clothing right off her form. When the light faded, Kat's groaning, naked, agonized body slumped down the wall and sparked a few times. Kat had never felt magic like this before -- surging into her completely from the outside, with none of her own power to counter it. Raised bumps appeared on her belly, all the way to her crotch, which tingled in the cool air of the room. Moaning, she ran her hands down her torso, trying to feel what they were. It felt like touching her nipples. Tracing down further caused her leg to kick out and begin to flail around. Embarrassed, she stopped, but was immediately assaulted by an electric surge of magic toward her legs.
Her feet stretched out long and thin in front of her, bones cracking, pinky toe dissolving, big toe shrinking slightly, other toes swelling noticeably and puffing up underneath. A piercing prick of pain through her cuticles accompanied her toenails curling into cylinders and then into thick, hooked cone shapes. Claws sticking out of the rear paws of a dog.
Kat gasped when her elbows slammed against her body and her upper arms began to shrink. She could no longer move her shoulders as she was used to. She was forced to hold her forearms out in front of her. And then her hands began to shift. The palms began to lengthened, but the fingers were soon to shrink. The opposable thumbs she'd grasped everything she'd held with were suddenly limp. Pads formed, and another shot of pain resulted in new claws. "Please, no, not my hands, not my hands," she called out, weeping. "Keep my magic, but let me keep my human hands." But Janice and Margaret didn't flinch. If anyone needed to carry a food bowl or open a doorknob for Kat, it would have to be a human. If Kat needed to hold anything for herself, it would be with her mouth.
Speaking of Kat's mouth, it was getting longer. Her jaw creaked out in a terrible nails-on-chalkboard noise, and so did roof of her mouth and the mass of bone above it. The vibrations through her skull were mind-rattling. Soon her mouth had caught up with her nose, which had broadened to cover much of the end of her increasingly snout-like face. It was not even close to over; the lengthening muzzle creaked out even more forcefully until it stretched out broad a flat in front of her eyes. She tried to say something, tried to tell them she'd be a good daughter if they'd stop this, but open her mouth just let a dog like-whine and a long flat tongue tumble out. Her mom had heard Kat say her first word, and now Kat would be reduced to barks and whimpers from now on.
"It's for the best this way, Kat," said Janice. "No one needs to know you were my daughter. You can't expose witches or our ways even if you do end up remembering. And I can maybe learn to love you again as my forever little girl."
Kat said nothing. There was no point. She began to sniff the air through her dampening nose. Her mind seemed to want to tell her what she was smelling but just needed time to sort out its olfactory abilities and sensory instincts first. Tears stopped falling from Kat's eyes as they lost the ability to cry like a human, but she would have wept a river when the colours drained out of her vision and she could only see that blue and not-blue. A dog doesn't need the tapestry of colours a human would experience.
Kat tried to stand up. She wobbled up onto her four paws and tried to stand on her back two. But she quickly fell forward, her fore-claws clattering against the floor as her posture returned to its new normal. Her ears popped, and Kat yipped, suddenly everything was too loud for her. The magic grabbed hold of her ears and ripped them almost out of her skull it seemed -- but they weren't detaching, just lengthening widening, and flopping over beside her, until she could feel the floppy things dangling against her fuzzy cheeks.
Wait, fuzzy? Sure enough, light-coloured fur was starting to sprout all over Kat's naked body. She whimpered, feeling the tingle as it grew in. She wanted a reprieve from this fur growing, but instead she had to endure her backbone starting its own growth, forcing itself out of her pelvis only to dangle down over her ass. A tsunami of feeling rushed back up from the end of it, and she instantly could feel all the way down from the base to the tip of her new length of vertebrae. A jolt of motion told her new muscles were kicking into action, then a sudden fear-induced reflex tucked the long thing all the way up underneath her belly, tickling her underside with its own fresh code of dog fur. Kat didn't even half to look back to know that this was her dog tail, a clumsy fifth limb that would trail behind her all the rest of her days, following her all the way to her grave.
The magic left Kat's body, and she barked. She wished she could talk again. "Oh, what a pretty yellow lab you are!" said Janice. Kat growled, but Margaret reminded her: "You don't have to be part of this family, remember that. If you bite or otherwise attack your new owners, they WILL send you to the pound." Kat drooped her head at her grandmother's words. She left trotting on all fours behind Janice, her owner that used to be her mother.