I saw my teachers vagina!?

Ok so today I was in summer school, and my teacher was reading to us. She was wearing a semi short (above knee about like probably half an inch) skirt. We were reading, when my friend tapped my shoulder and pointed toward her direction, I looked, and she had her legs spread, and YOU COULD SEE HER NAKED VAGINA!!! Ewwwwwwww! She's like 50! That's disgusting and I don't know what to do or what to think of it. Was she trying to turn us on? Could it have been an accident? Wtf? I'm only 15 and I KNOW WHAT MY TEACHER LOOKS LIKE DOWN THERE NOW! EWW! What should I do?