View the Gallery / 15 Photos »

Shanae Grimes not only denies dating John Mayer, but even managed to bruise the celebrity serial dater‘s ego too!

“According to Star magazine John Mayer and I are in secret sexy cahoots,” Grimes (pictured filming her role as a homeless teenager on the set of Sugar in Los Angeles) tweeted yesterday. “How wonderful for me…if wonderful meant embarrassing.” Ouch. Looks like Mayer has experienced a very different kind of napalm attack from the 90210 star.

Mayer’s camp is keeping mum.

“They are not dating,” a close source said, followed by the singer’s rep who added, “Star magazine is not a credible source.” I think a 21-year-old B-list celebrity calling the mere idea of going on a date with you embarrassing is credible enough for now. Case closed.