Selina awoke the next morning to find herself curled up in a cat-like posture, laying naked on her bed. At first she couldn't remember how she had gotten there. Then she remembered arriving home from last night's burglary and seeing her reflection in the mirror, the jeweled eyes on the cat necklace sparkling back at her. She didn't usually sleep naked but something about the reflection had almost hypnotized her. She realized she was also still wearing the necklace.
She realized everything looked a little odd, like there was something slightly different about her eyesight. She rolled onto her back but immediately felt uncomfortable. Something seemed to be pressing on the base of her spine and the sheets seemed to have bunched up uncomfortably between her legs. Then they moved and she realized it wasn't the sheets at all - she caught sight of a tail!
Selina tumbled out of bed with surprise, landing surprisingly nimble even for her. She examined the bed but nothing was there. She felt the odd senstation at the base of spine again and reached back to touch it. She found the tail belonged to her, extending several feel from the base of her spine.
As she got up, she caught sight of herself in the mirrior and realized several more additions: her breasts were as perky as ever but now she had 6 of them. Her eyes resembled those of a cat, which explained her eyesight. Her black hair seemed longer and wilder. And her tail swayed and twitched behind her like a cat. Her fingers felt funny and some flexing of her hands made her realize her fingernails could now extend and retract like a cat's claws.
And the eye jewels of the cat necklace twinkled back at her in the reflection.