Should I tell my parents that my cousin did this? It's insane!?

My cousin had an orthodontic appointment to get her braces tightened. We live in a small town so her parents had to drive two hours to go to the appointment. I decided to come with them to get some shopping done. When she was standing in the waiting room no one else was around except her and me and I saw her reach her hand down her pants and scratch her ***. When she brought her hand back up it had gross white stuff on it and she just wiped it on the door handle that everyone coming in to the waiting room has to touch. I was grossed out and I asked her what the heck it was and she said it was "vag goop". WHAT THE HECK IS SHE TALKING ABOUT? I thought it was disgusting I wanted to barf. Should I tell my parents or hers? She just laughed.