If we do truly, what we feel in our heart?

And it is said that christ lives in our hearts. How can it be wrong? My girlfriend moved her from Alabama, She had been married for 20+ years. She decided a long time ago her marriage was over. The only reason she stayed, was for her daughter. We came to be, under extraordinary cirstances. We new each other in high school. We both agree, due to the cirstances, that the good Lord is what brought us together. She has recently signed her divorce papers, after being with me for 11 months. Her brother, has never wanted us together because it takes time away from him that he feels she should spend with him. We both know within our hearts fully, that we do truly and very strongly love each other. We both want to be together. About 35 days ago, her brother started telling me that she was seeing other people. At first, I blew it off. But as persistent as he was,Everything he was telling me coincided with what she was doing. It made sense. Keep in mind, everything her brother was telling me, i was telling her. I was not questioning her, but i was keeping her up to speed on every word he was saying. After about a week, she left me. She continues to see me, but she says she cannot live with me. She says she is under conviction, even though she loves me, and wants to be with me. How can that be? I had a southern pastor tell me once, " You always listen to your heart, it won't lie to you. But your mind, will mess you up every time. " How can she feel like she is under conviction and still want me, love me, and sleep with me?