Well, as to the first part, I think she was too out of it to do anything by herself. He had to pick her up and carry and drag her from Smallwood to 5N. Maybe she wanted to go with him, maybe she didn't. I don't think it matters. She was too intoxicated to even walk, let alone make decisions or consent to anything. He should have left her at home.
I don't know about the altercation. It's a good question. I believe the story that the witnesses told the investigators, that they didn't like what they saw and said something to CR. I can only guess at the rest, but based on the story and what I've seen of CR's attitude, my guess would be that ZO's reaction wasn't just about protecting Lauren, but also about being told to get the eff out of his way or whatever CR said. Maybe those guys thought she was going home after that. Or maybe they were distracted by their own egos. Or maybe they thought it was a big enough deal to say something, but not a big enough deal to call the police. The witness was in the same situation a few minutes later -- What do you do if see something that worries you enough to speak up, but the person reassures you things are under control? I guess you make a quick judgement call about whether or not you should involve yourself further in the situation or can believe that things are under control and he's going to take care of her.