How do I go about this situation?

, when I had a boyfriend, I did not go in my room. I stayed in the living for my mom to see me. My friend lays in my bed with him and they go in the bathroom together, they're not doing anything but it's disrespectful in some else's home. Especially when she's under the age of 18 and her parents don't play that. When she sleeps over, she sleeps in the bed with me but one morning I woke up and found her laying on the couch with him. They were both on opposite ends but I still did not like that. My mom has spoken to me about it and expressed how she doesn't need to be doing all of this and I agree with her. So that's why I'm going to talk to her about this tomorrow. I just don't know how to go about it and how to say it. Any advice or tips?