She becomes an anthropomorphic animal.

As Jack left the table and Kelly began to clean up alone, she would begin to feel strange... warm inside, and dizzy. She rubbed her head, stumbling back to brace herself against a nearby counter, feeling an alien shifting feeling within her. Something unnatural was happening to her body, her anatomy changing shape in impossible ways, and she was helpless to resist, simply moaning out.

Jack, in his room and deciding what game he would try to spend time on, would hear a sudden cry from his mother and rush out to see what was wrong, only to freeze at the sight before him.

Kelly Rayson stood, panting and confused, having transformed into an anthropomorphic version of some creature... the question was, what had she become?