Soooo, what would you do!?

I recently found out my friend is what's known as a "little," She said she identifies as a 2 year old, wears like baby onesies in adult sizes, wears a diaper, uses a pacifier/sucks her thumb, and apparently she's been seeing this 55 year old guy.. we are both 19, and I can't help but to feel like a little weird about the situation. She told me because she wanted me to come to her "daddies" house for dinner this weekend. and only told me because she will be in her "little space" which I guess just means she will be role-playing as a child from the way she explained it to me. I don't know if I can handle going to this dinner without looking at this dude like he's some kind of pedophile. Like she's already 19, that's more than enough of an age gap for this guy to be her actual father.. she's also a very small petite girl already, like 4'11, very slender, and her and I joke about her being the president of the itty bitty titty committee because she's flat chested. idk, part of me wants to pop her in the back of the head and tell her to get it together, the other part of me doesnt want to be so judgemental of her but it's so so so uncomfortable for me, and she told me she lost her virginity to this guy when we were sophomores in highschool and they had met through the casual encounters on Craigslist. I just don't know how I didn't know any of this about her until now and I'm questioning our entire friendship now.