So if I follow this, your mom thinks you are having sex with your best friend, and your sister, and a middle aged man and keeps making jokes and/or screaming about it.

Uh, no you're not sensitive your mom is an awful person.

I would say she's just teasing you except for the part about sleeping around with your sister. That sounds deeply weird.

If it's possible, when she starts, just leave the room. Don't react - just leave.

You're not wrong.

so this is confusing and gonna give it a shot.

If you are not in a relationship then who has the right to say who you are sleeping with?

She is suffering from some kind of delusions it sounds like. I had someone accuse me of the same thing but they had a mental illness.

Is mom a narcissist???

It sounds like she's doing this for a reaction to me... don't engage with it and just walk away.

Yes, these aren't funny jokes, they are invasive and unpleasant comments which serve no useful purpose.