A little mistake

" Remember what I told you about how this thing works. Judy, your hands are full. I'll just put it on you," offered John. Judy felt a tingle when John put the medallion on her neck.
"Hey John, can you get the bathroom door? I want to change, but not in the living room. I think it would be fascinating to see my crow's feet disappear in the mirror"
John opened the bathroom door and then closed it to give his sister privacy. He sat on the couch, crossed his legs and went back to watching cartoons.
Judy decided to strip down so she could see this change in action, and make sure she had clothing on had to change her back to herself. She took a few seconds and looked at herself in the mirror, feeling like she had let herself go a bit. When she was in high school and college, she was the envy of all the girls. Her husband used to buy her sexy lingerie and skimpy bikinis. When she got pregnant and had Alice, she had a lot to juggle and going to the gym took a lower priority. She had to admit she still looked good, but there were some stretch marks from the pregnancy, a little pooch an her breasts were not as pert as when she was 22. She took out her phone and took a picture so she would know her baseline. She touched the dress to the medallion and waited.
After a couple minutes she noted her face looked a little younger and the wrinkles around her eyes looked a little less. She looked at her fingers and felt they were more dainty. Her hair slightly longer, which was odd since she had her hair cut the day before the event. She turned to the side to see that her stomach was definitely flatter. She leaned forward and took a closer look. Her hair was definitely longer and lighter in color. Something was wrong, so she took off the medallion. She looked in the mirror. She looked younger than she meant to, but also slimmer. She realized she was a little shorter and her hair was almost as blond as John's.
"That shock from earlier must have started the change," said Judy in a voice that was not quite her own. She put on her bra and panties, but found that they didn't fit right anymore. She put on the dress that she meant to use, and realized that it would have to do. She folded everything else and put it on the countertop before leaving the bathroom saying "John, we have a bit of a problem."
John turned around to see a blond woman that looked to be in her mid twenties whose face looked almost like his sister's.
"Well, you are definitely younger Judy."