There were so many choices, and Mary didn't really know what any of them would do, but she found she had a craving for chicken. Remembering how delicious the "woman" vials had been, she figured the chicken one would be equally good, so she plucked it out of the case and started drinking it.
Her stomach jerked violently as she drank, causing her to drop the vial when it was still half full, so she didn't get the full dose. It hadn't tasted like much anyway, so as far as her cravings were concerned Mary didn't mind, but she didn't have a lot of time to think about that anyway before the changes started.
Her bulging belly had only been the first symptom. The kicking stopped, which concerned her for a moment, but it was replaced by another sensation that Mary couldn't identify. Curiously, she pressed her hands against her belly, feeling several odd shapes in there, but her investigation was interrupted by an intense urge to remove her socks, shoes, and pants. It was something deeply instinctual and Mary couldn't deny it, so she stripped halfway. Even before she was finished, pin feathers started pushing through the skin of her belly and she felt a pressure at the base of her spine. Gasping--it hurt!--Mary reached behind her and felt a small nub of a tail that was also rapidly becoming feathered.
Before long, downy snow white feathers covered her from just below her breasts to mid-way down her thighs, and larger, heartier feathers were beginning to layer on top as her lower body reshaped itself, forcing her to jut out her chest a little bit to accommodate for the way her new rear end shifted her spine. Her tail feathers spread wide as a new sensation overtook her legs and she looked down to see her pinky toes completely shriveling and falling away from her foot, her remaining four toes splaying painfully as her big toe took up residence at her heel, which was itself rapidly shrinking.
All muscle definition was lost as the skin of her legs and feet became yellow and scaly, her toenails lengthening into talons along with her toes. It was almost like she could feel her legs and feet sucking in as they became the feet of a hen. It was painful but not unbearable, and when it was finished, Mary inspected herself in the mirror. She was exactly half of a white hen which must mean--
Gently, she palpitated her new feathered belly, her clawed feet scratching the bathroom floor. Eggs. She was full of five eggs. She had to build a nest--it was an instinctual desire she could not deny. She headed out into the living room, gathering blankets, sheets, and pillows along her way, and found a nice open spot in a corner where she began to spread and pile the linens, pulling here, tucking there. At last, she was satisfied and stepped with her new legs into her nest, then roosted down, folding her arms over her bird belly.
Here, she would lay her eggs.