My (36m) girlfriend (26f) left me stranded and cheated, amid I dumb for wanting her back?

My girlfriend of the last 8 years left me at a friends house, in a differnt town from where we live, and took off with some random guy, couldnt get ahold of her, and when I did she was short with me. I already know she cheated cause my gut just knew it, when I brought it up to her she admitted. She still with the guy and tells me she doesn't wanna go home yet cause shes thinking about life. Am I an idiot for wanting her back, am I lying to myself thinking she will come back. She tore my heart out and dont care so why do I still want her back? What's wrong with me why do I still want her to come back?