Mick Hutson/Redferns; NFphoto.com The relationship between rocker Nikki Sixx and Denise Richards has reportedly ended. The two went on a few dates and it seemed like they really liked each other, especially when Denise extended an invitation for Nikki to spend Christmas dinner with her and ex-husband Charlie Sheen. It seems that Nikki didn't take her up on that offer, which means he must not have been that into her because, really, who would turn down an offer to dine with Charlie Sheen? Sixx spent New Year's in Mexico with his children, while Denise spent it in Hawaii with her children, but even then they still had something brewing because Sixx tweeted for "@Denise_Richards to get her butt to mexico...J" Maybe the relationship came to a screeching halt when Rock and Roll later rejected Nikki Sixx from ever working again for using Twitter...and a smiley face.