As her tail finishes growing, slowly, painfully, the agony shifts.
"Come... come on... gimme a... friggin' break..." Mary grunts, dropping to her hands and knees and forcefully vomiting as her body itself starts to change, her skeletal structure slowly widening to accomodate a heavier frame.
Sweat beads down her forehead and sticks to slowly growing brown fur.
"I... don't... wanna be a cow..."
That's when she hears it. A voice, inside her head.
[Then you shouldn't have drank of that vial, Mary. You gave birth to me, and now you and I will be one, and there's nothing you can do to stop it. After all, don't I have the right to exist? Don't worry, you'll like being me.]