Oh gosh this reminds me of one of my most squirm making experiences.
I had a flatmate, and she asked me to help her change the bed, she had injured her back so I said, yes fine, normally we didn't help each other change our own beds.
Anyhoo, stripped off the bed and the bottom sheet was the most amazing set of various stains, like a Rorsauch test! I was a bit yuk-embarrassed but she started blithely pointing to each stain and telling when, how, the position, length of time, with distinct pride.
I moved out a bit soon after that, but really, if you had thrown that bottom sheet at the wall, it would have stuck there.
It is yukky, so YANBU.
Also, yes, if your friend is going on and on about it she seems to want some form of validation.
Once the same friend entered into a threesome, once it was at a open air concert in Kew gardens and a colleague from work said "Christ, throw a bucket of water over them", he proceeded to find someone's champagne bucket and do just that.
The champagne had already been drunk, I add.