My Girlfriend's Mom

I have a girlfriend with whom I have had a relationship of almost year. We like each other. Last month, she took me to her home to meet her mom. Her mom is a sexy lady. After seeing me for the first time, she became addicted to me. She often kisses me on the lips when my girlfriend is not nearby, but when my girlfriend is near, she gives me kisses on the cheeks. Last Saturday, I went to meet my girlfriend. I knocked on the door and her mother opened it. She told me that my girlfriend was not home, but that I should wait. We chatted for an hour, and then while talking about love and sex, she kissed me. Both of us kissed passionately and made love for half an hour. She is so sexy and kisses better than her daughter. I liked her from that day, but I cannot betray my girlfriend. I don't know what to do.

— Ned, 25