Yep, it works

Sarah found a perfect parking spot as they finally arrived at the beach. Jennifer hopped over the side of the car, her boobs jiggling hypnotically as she got out.
"Wow, Jennifer. I think your tits have SO much more bounce than mine." Karyn slid across the backseat and groped at her best friend's chest.
"Yeah, but yours are shaped so perfect!" Jennifer giggled. Neither of them were paying any attention to Sarah, as she grasped the stone close and whispered a wish. Something simple, just to see if it worked again.
"I wish I had a cold pepsi."
Instantly, a can of soda appeared in her lap. It sent a shiver through her body. This was great! Still holding the rock, she got out of the car and tossed the keys and the rock in her beach bag.
"Alright girls, let's go! I think today is gonna be awesome!"
Karyn and Jennifer followed her to the beach. David Ruhan, a senior in school, noticed them first. He strolled up to three of them and introduced himself. Sarah teased and chatted with him and Jennifer urged her on.
"David's always liked you! You should see how he looks at you in class!"
He was tall with blone hair and green eyes, good build.
"Yeah, so how about we go get a drink girls?" he urged them to the juice bar. As Sarah bent to pick up her beach bag, he reached over and grabbed her butt. Just a quick touch, but Sarah felt herself getting hot. That bastard! Sarah reached into her bag and clutched the rock. "I wish that David was female from the waste down!"
David was talking to Jennifer, laughing cooly about something. Suddenly, a powerful surge of lust pounded through him. He reached down to his crotch, where he found his swimming trunks tightening into a pair of white thong panties. The front pulled tight over his cock, which was quickly smoothed away into a femine mound.
"Oh. My. God!" shrieked Jennifer, "That is just THE perfect thong! It looks SO good on you! Where did you get it?"
Stunned for a second, reality quickly caught up with David. "Oh, I can't remember. I think I found it at the mall."
Sarah grinned. David was still competely male from the waste up. But below that was pair of sexy legs, a pefect ass (that, she had to admit, she was a little jealous of), and a tight silver thong that showed it off while covering his crotch.
This was perfect! One of David's male friends passed by and said hi, without noticing anything weird at all. Sarah grinned