Is it disrespectful for another girl to sit on my boyfriend's bed?

My man "G" has 2 rm mates. There's a girl who comes by almost every other day. She said she comes by to hang with them all, no one in particular. One day i came in and she was sitting on G's bed. Ppl hang out in G's room since he kps the cleanest room. I didn't mind her being there, but there were 2 chrs in the rm and thought it was disrespectful for her to be on the bed instead of using a chr. I spoke to him and he said she was annoying and he never paid her any mind but he would talk to her about it. one day soon after, She got ready to leave and G asked her where she was going and why she was lvn. She went to the kitchen to the front door. He went in after her. 5 mins later I find them at the kitchen tbl tlking. I sat on his lap and put myself into the conversation. She was tlkn about how she was single and ready to be in love or some bs. I got mad that he even cared that she was lvn and said if she kp comin ova there, it would be drama. She seems to like him but G doesnt see it.