Why someone would lie to someone and say, nobody loves you.?

Years ago I once tried to convince my girlfriend that I was not lying and that I was a good person. Then she threw me curve ball at me, the whole nobody like's you line. No one she knew knew me except one girl friend of hers from long ago that she couldn't even keep as a friend. I didn't have time to make friends with her new social network. She was judging me harshly talking behind my back and never giving me the time of day to get to know me. In fact she didn't have any real friends. I watched a reality intervention talk show and they had some irrational drunk violent jerk of a woman say that line to her husband when she was judging him harshly and making false accusations that he was a pedophile. He was overly upset, emotional irritated by her so he would obviously fail the lie detector even if he was telling the truth. Why would someone lie and say things about someone that cares about them. Are they just so negative towards their own self image that they need to tear someone else down to their level just so they can build themselves up. Like making a lie to themselves to make themselves feel better and more able to be loved.