Two Girls Pooping

I was about 16 at the time and I was walking home from school with a girl in my class when I had to poo really badly. When I told her she dared me to do it in my knickers and I was tempted but I wasn't sure if I could trust her so I refused to do it. She said she was desperate for a poo as well and she would do it in her knickers if I did it in mine. I still didn't trust her so I told her to go first and she said I had to do it first. We ended up in a stalemate and as we walked I noticed my classmate was slowing down and she told me she couldn't hold it any longer. I was scared she was trying to trick me and when she asked me if I was going to do it in my knickers I got really suspicious and I said no. Then I could smell poo and bits of it were falling out of her knickers and she wet herself as well. She begged me not to tell anyone about it and I promised her it would be our secret as I relaxed and immediately felt relief as I filled my knickers with a huge load. I peed myself as well and as far as I know no one knows about the incident.