Tony Romo and the brunette: Jessica Simpson on notice

Jessica Simpson's boyfriend has been accused of cheating on her. 02/10/2008 - Tony Romo - With the party in full swing, it is alleged Tony - who has been dating Jessica since November 2007 - disappeared upstairs with a stunning brunette for the rest of the evening. © Image of Sport / PR Photos

02/10/2008 - Tony Romo - With the party in full swing, it is alleged Tony - who has been dating Jessica since November 2007 - disappeared upstairs with a stunning brunette for the rest of the evening. © Image of Sport / PR PhotosAmerican football player Tony Romo reportedly visited Hollywood hotspot My House on January 16 - hours after the 28-year-old singer has flown out of Los Angeles - and then invited a group of people back to the home he shares with Jessica.With the party in full swing, it is alleged Tony - who has been dating Jessica since November 2007 - disappeared upstairs with a stunning brunette for the rest of the evening.A source told America's Star magazine: "Everyone was talking about it downstairs. The girls were saying it was so wrong and shady of Tony to cheat on Jessica - especially in her place! I just can't believe he would hook up with another woman at his own girlfriend's house."Neither Jessica or Tony have commented on the claims.Jessica has recently been the subject of scathing comments about her seemingly fuller figure, prompting her sister Ashlee to leap to her defence.Ashlee wrote on her blog: "I am completely disgusted. Since when did a woman's weight become newsworthy? How can we expect teenage girls to love and respect themselves in an environment where we criticise a size two figure? "I find it completely embarrassing and belittling to all women to read about a woman's weight or figure."