Justine had an idea. She entered her room and smiled at the stallion-boy. "I've been waiting for you, too. Take me! Take me as your own!"
Jesse smiled and pressed his cockhead against her pussy as he began to work his way in. "That's just what I wanted to hear..."
He had no idea that the mare was holding back, saving up her mental will until she could take him by surprise. He slid his long, rough horse cock all the way into her, and still she only moaned softly.
Justine wrapped her legs around Jesse as he pumped into her fiercely. As pleasure clouded the stallion's mind, Justine could sense that he was letting his guard down. She timed her transformation perfectly to catch him just before the moment of orgasm.
Jesse jerked back in surprise as Justine's form began melting down. She became a quickly-growing, tan-colored goo-form that pulled Jesse in. Her form again shifted and tightened around him, absorbing his body and will into herself.
When the struggle settled down, Justine had become an anthro horse dickgirl, even taller than Jesse used to be, with a full set of both male an female equipment and wide feminine curves.
"Well, that's the end of that." Justine said to herself as she began to stroke her new horse cock. "I wonder what people will think when I come to class tomorrow. Heh heh..."