Dream of girlfriend

My girlfriend has been having dreams about other men a lot for the past few weeks. The first time she told me she felt guilty afterwards and I was like ok....nightmare, that happens. But today she told me she had a dream of someone who she was REALLY in love with and she did really dirty things with him, and she told me he looked at her like nobody ever did before and said things to her...like it was the best dream she ever had sexually too...and in her dream she lied to him about me and kind of put that guy before me...she was really happy in her dream. That guy in her dream told her all the things that I don't. I'm really upset about this I don't know what to think I really need some answers here...