If the fight began in the lobby of LS's building, perhaps CR refused to take LS to her apartment (5th floor?) because not only was he not allowed in the building, but because he thought he might get jumped or assaulted by JW's friend/s if he moved away from the Smallwood lobby...and apparently, he did.
Who knows. You could be right. Apparently everyone involved was drinking heavily, thus Corey was "put to bed" by his roommate. It's hard to know whether anyone was acting rationally at that time. Interestingly, her friends had never met Corey before. Did she first meet him that night?