I think the fixation on drawing the implication of a rift in the relationship from LS and CR's being together late at night is unwarranted. Are college girls with boyfriends not supposed to have a social life, even a "party" social life, apart from their boyfriend? This seems unrecognizant of the nature of these individuals', if not most college students', social lives - we have been told by her best friends that LS had an enormous circle of friends and was a social butterfly. They have also told us she had a great relationship with her boyfriend, who appears to have a similarly wide social network.
If you believe JW's alibi at least up until 2:30AM (and we have no report that he was among the group at Smallwood at the time, though that doesn't mean 100% that he wasn't), JW was obviously insufficiently concerned about being apart, and not hearing, from his girlfriend, who he sees all the time, even late at night on a night they were supposed to meet, to go looking for her.
1. CR wasn't a friend, he was a recent acquaintance. That changes things A LOT.
If it were a good friend, she might hang out with him late, but a guy she had just met?
2. CR at the very least had his hands all over her, and possibly they were kissing, making out, etc.
(reported by a witness in one of the early articles)
3. The boyfriend's friends beat CR up, which also indicates Lauren and CR were more than just platonic friends.