I’ve known my gf’s roommate for a few years now and we’ve all become good friends. She is single and the three of us regularly hang out. I spend the night at their apartment a few times a week.
They’re both pretty open with their bodies, changing in front of each other, one will shower while the other is doing her makeup, etc.
There have been a few times where I’ve seen the roommate in her underwear, in a towel, topless from the back. But nothing crazy.
But over the holiday weekend she seemed to get a whole lot more comfortable. First she “forgot I was in the room” on my computer and stripped her clothes off down to her thong to try on a dress for a New Year’s party. My gf jokingly yelled at her and I turned around and got an eyeful of her boobs before she covered up.
Later that night we came home and she was a little tipsy and changed with her door open into just a t shirt and thong and came back out in the living room to watch the ball drop with us. She got under a blanket but made a comment like “it’s nothing he hasn’t seen before”, and my gf just laughed it off.