The 25-year-old singer has been dating 30-year-old Taylor Kinney since meeting him on the shoot for her music video `You and I` but pals are worried `The Vampire Diaries` actor will cause her heartbreak after his former girlfriend accused him of being a cheat. A source told America`s Star magazine: "All of her friends are telling her to watch her step - Taylor is bound to break her heart. It’s only a matter of time before he finds someone else." Taylor`s ex Brittany Sackett - an estate agent from San Diego - has claimed she was still in a relationship with the actor when he first started dating Gaga, who split from her lover Luc Carl for the second time earlier this year. Brittany said: "She was with my boyfriend, and I found out he was cheating on me." The pop megastar wrote `You and I` about her Luc and she recently admitted she gets emotional when she sings the song because it brings up memories from their relationship. She explained: "There is not one song on any of my records that wasn`t written by me, and I think when you write your own music you find ways to reinvent [the songs] emotionally through yourself and performance so that they are different every night and that song you know, sometimes it`s about the guys and sometimes it`s about the fans."