Saw GF's mom

When I was in high school, I was at my gf's house early on a Saturday morning. We had been dating about 6 months and I think her mom approved of me. I arrived a few mins earlier than I told her I'd pick her up. Her little sister answered the door and ran to get my gf. While I waited for her in the living room, her mom came walking into the kitchen naked. From the living room couch, I saw her from head to foot. She screamed when she saw me and ran to the back of the house. She claims to have not known I was there but I've always wondered if she really knew and wanted to create a flashing situation. For months we laughed about it but she never admitted anything.