A childhood belief about periods

This isnt about my belief but my friend's little sister. When I was in 9th grade I was staying over at my friends. Her 8 year old sister, being as nosy as she is decided to go though my over-night bag and she came across a pad and asked me what it was. Since my friend wasn't in the room to explain it to her and I tend to be shy around that kinda stuff, I simply told her it was a napkin. Of course she knew what a napkin looked like so she didn't believe me so I told her it was a special napkin and I took it away from her.

Later that week my friend came to school and asked me why I told her that. I didn't know why she found out or why she would even care but she said that the night before her first real boyfriend had come over for dinner to meet her family. Her little sister then mysteriously disappeared into the bathroom and brought out a napkin and gave it to her boyfriend saying that "They were special napkins and since he was the guest he should get one." Her mom was then forced to tell her about periods while her boyfriend was there. I found it pretty funny but she said she was so embarassed. We laugh about it now though.