Sweat beaded on Kelly's forehead, as fur began to grow down from her hairline as her nose began to broaden, leaving a nice white streak down her growing muzzle as grey fur grew across her darkening flesh. The changing woman's asshole began to pucker, the flesh expanding and growing larger and darker until it was indistinguishable from a horses' asshole. The dark color beginning to trail down to her pussy as the lips darkened to a leathery black while the insides were an inviting pink.
"Oh~ oh fuuuck!" She whinnied as her clit grew larger with her pussy, winking for the first time as a dollop of arousal leaked between her growing thighs.
In her reflection in a puddle of water in the stall she could see what she was feeling as her chest barreled out, each breath becoming deeper and stronger as her organs began the shift from human to horse. Samson could smell the changes as his upper lip curled up, drinking deeply of the mares scent as her bent his muzzle down and huffed between her growing ass cheeks. The sensation made Kelly whinny, her nose flaring as it grew dark. Samson began to lick Kelly's new mare pussy as she gritted her teeth in the sheer pleasure from his actions, her body beginning to pack on dense muscle, she felt more powerful than she ever had before.
"Yes, I'm such a powerful mare, Samson is the perfect mate, our foals will be so strong~" She thought to herself as she looked at her reflection. Kelly's ears were beginning to grow out from her blonde hair as it began to turn black, tilting her head to the side making her neck pop as it grew stronger and more horse-like. A trail of her new mane beginning to grow from her hair line.
Samson, now hard as a steel rod, finally began to mount her as Kelly's flanks grew incredibly strong, with a growing tail covered in black fur. He took a couple of jabs before his cock finally dove deep into Kelly, making her whinny before craning her head down now powerful enough to easily hold her stud's weight up.
Looking down at her reflection, she could see her eyes shift and become those of a horse as her head finally began to take equine proportions. "Yes, this is what matters, I have found such a good stud, we will have the healthiest foals I must grow his herd!" She whinnied hard as she felt the first ropes of Samson's massive orgasm paint her needy mare womb full.