When I put my foot on it

Last holiday I went to a fifteen party and my friend asked me if I wanted to sleep at his house with another friend of him, Gabriel. As soon as we entered in the car we started to talk about the party. There was a girl whom my friend think she's beautiful and I knew some stories about her. I started to talk all I knew and believe me, it wasn't good things. When I said her name, Gabriel got surprised and said ' oh, she's my girlfriend '. I didn't know what to say in that moment, I was so embarassed. I apologized him and stayed quit the rest of the way.