Marcus snorted up at Jon. "About fucking time, 'mano. Me and Caperucita Roja here were just talking about my hair. Where the fuck've you been?"
This was said jovially, rather than in an accusing way. Marcus knew as well as Jon did that the man wasn't late. He budged over, as well, but there was certainly more room on Susie's side. Marcus had a way of taking up a lot of booth. By way of sloppy introduction, Marcus added, "Jon here's looking to get fucking married or some shit. You pick out your fucking ring or whatever, yet?"
It was his equivalent of this is my friend, Jon, who happens to be in a serious relationship with someone. Susie didn't look like she was fishing, really, but still, it seemed polite to let her know that Jon likely wouldn't take any bait so that she didn't feel the need to try. She could just relax and keep drinking.