From all of the stories, here's some good working assumptions:
1. Lauren and b/f JW are in a fight of some sort, or had broken up.
(did he graduate?...maybe she is looking for her next IU b/f when he leaves?)
2. For some reason (perhaps an online or phone fight with JW), Lauren suddenly leaves Smallwood to go to 5 North.
Did she go there to pre-party with JR? Or to meet up with recent male acquaintance CR?
3. She spends 45 mins at the bar and gets kicked out for being completely wasted/loaded.
4. She was either already with, or somehow meets up with CR, they get touchy-feely with each other, and head back to her place.
5. Her boyfriend's frat brothers confront Lauren and CR at Smallwood, punch the guy for having his hands all over Lauren,
and CR bolts out of the building, with Lauren following him.
6. Lauren is seen walking with a male (presumably CR) back to his room at 5 North.
7. Although the official story is that Lauren helped CR's roommate MB put CR to bed from his injury,
considering that he had no real signs of physical injury, nor did he ever consult a doctor about a concussion, this story is possibly bogus.
Maybe they fooled around, maybe they drank / used drugs, or maybe CR did indeed go to sleep.
8. After she's done with CR, Lauren heads a couple doors down to her friend JR's apartment.
At the very least, we know that JR, his out of town friend, and Lauren were in that apartment.
There could have been more people, either for the entire time, or part of the time Lauren was there, we just don't know.
9. ?????
Either, as JR says, she decided to go home around 4:30 a.m. and he watched her round the corner on her way home,
or his story is simply not true.
Conclusions:
Either something more nefarious happened at 5 North, and Lauren never left JR's apartment alive, or at least did not leave that building alive,
and JR and/or his friend and/or other persons know what happened to her,
Accidental overdose, or murder, or whatever,
OR
JW, very upset over relationship difficulties with Lauren, confronted her that night and killed her in an act of rage,
either after she left JR's, as he said,
or perhaps he even went to JR's that night and left with her.
I think those are the only possibilities that make any sense to me.