For the last year at my house (or rather at my mom's house, since I live with her. I can't live on my own yet) guests come over, her friends. In total there are usually 2-4 people. I think they are good people, but one of them is the most strange, he is rich, no children and I just have doubts about him (the fact that he and my mom have a lot of mutual friends, acquaintances, and other social connections, including my father (her husband). They are having fun, drinking alcohol and everything seems to be decent, but I'm pretty uncomfortable, even though I'm an adult, but talking about sex and so on and everything like that makes me uncomfortable. Because I do not understand who they are talking about, but they behave quite liberally. And now, for the second time after these "get-togethers" (and they usually last from evening until late at night, or even morning), I often hear that when all the guests have gone and my mom stays home with me (usually I hear her doing the dishes, and yes sleep over the noise does not work, I practically do not pay attention, yesterday, for example turned on the radio and I could not sleep. I had to stealthily take it with a wire not to turn it on). and then after that, I either do not sleep because I can not sleep, or I wake up at night and hear my mother crying. And she doesn't hide it much. It's like a roar or a woman's moan. And when she goes to the bathroom (I guess to cry even harder, but the sound of the water doesn't drown out her moans), it's really disgusting to me and I take it very hard. 

Anyway, I don't think you can help me with advice, but I'm just sharing here, because there is nowhere else.

And once again I will stress that I am disgusted by her behavior when I sit among the guests, but am forced to listen to something about sex or other cases. There my father cheated on her and left the family, I know that. But I would rather not know that she cheated on him with someone, why would I need that information? Especially without any embarrassment on her part. And so on. 

I don't want to wear rose-colored glasses, but I don't think that if a person drinks, acts slutty and is not ashamed of it, then he is an "adult".

And yes, she usually doesn't drink, or doesn't drink much. That is, this whole situation happens when her friends come over and so on.