Lily sat, her face an inexpressive mask until she felt it. A piercing pain, right in her temples. Her slender fingers went to her forehead, frowning as it got more and more painful. "Ow... ow!" she yelped, as she felt it, something sharp pressing into her fingers. "Get me a mirror," she urged the young scientist who'd injected her.
"I don't think tha-" "JUST DO IT!" she barked, looking up at him, unable to see but suspecting that on her forehead were curling out two bovine horns. The young man rushed out of the room as she groaned, the horns curling out into six inch long curls coming out of her temples. The pain was excruciating, so much that she didn't even notice her ears flatten and elongate, the pointed tips sticking out of her coiffed hair.
"Oh no," she whispered, looking down and seeing her chest distend, beginning to feel the sheer weight of it in her shoulders and back. Her flat little tits were accumulating mass at a terrifying rate. The young man came back with a hand mirror, pausing in the doorway as Lily looked up at him, her torso dominated by tits the size of her head... and still growing! "Help me!" she implored him, but he only held the mirror up to her wordlessly, unable to speak. She could see herself, ears twitching, horns upright, nipples thickening and stiffening until she had a pair of thick teats atop what must have been K cup breasts.
But the real horror hadn't even begun yet. Suddenly Lily's entire body flashed with pain. She squealed as she looked down and saw her entire lower half just... growing! Her legs split into two each as she felt her ass moving further from her body, skin rippling as white and black fur sprouted. "N-no... I'm... I'm becoming a cow!" she whimpered, as she realised what was happening. Her four feet cracked and hardened, as she found herself clopping on hooves in the small room, her height increasing somewhat as she found herself atop a cow's lower body, her waist replacing its head at around where the neck would have been. She could feel an enormous udder dangling between her hind legs. "I... I..." She felt something in her throat, and tears welled in her eyes. "MOOOOO!"