Okay, regarding the boyfriend:
I can see why some people would suspect him. Personally, I don't see anything too weird in their behaviour, they are pretty young and Adrienne seemed to have been kinda jealous, so her "causing a scene" by getting out of the car etc. is understandable. I met my share of, uh, fiery women, especially in that age.
However, if we consider the hints that one or more of the party guests may not tell the whole truth, then it becomes questionable if she indeed ever returned from the very first trip to the boyfriends home.
Her clothes end up in her apartment.
Someone drives her car in an extreme hurry, manages to kill the front tires and has to drop it off a few blocks from her apartment and can't drive it to wherever it was intended to go.
Someone makes the calls to her bf (her bf's phone), who doesn't answer, and then the cab calls.
I wouldn't take cell phone pings alone as a clear indicator of position of the owner. E.g., if I were on the way to my apartment with someone, and unexpectedly end up killing my passenger, I could leave/drop off our cell phones at my apartment and then go and dispose of the body. After that, return to my apartment, pick up the phones and pretend to bring my victim home or whatever other scenario I want to create.
Criminals in this day and age usually know about cell phone pings, and quite a few have used it to try to hide the true events.
The problems here: LE should/would be very aware that a phone is just that, a phone, and would not just rely on that and if they consider some witnesses at the party unreliable, they would verify the timeline prior to her return to the party with the same scrutiny as when she returned from her accident.
Also, the story itself is too complicated. If the bf had some people at the party lying for him (like that friend of Adrienne who talked to her outside her apartment), there'd be no need for the "she got out of my car" part, he could simply claim that he dropped her off at her apartment and the other people who are in on it would confirm they saw her. It wouldn't also work as an excuse for "his prints on her phone", IMO, as there can be a million reasons for his prints on her phone, as he was her bf; and if he had anything to do with her disappearance, he could just wipe it clean before throwing it out, something the real perpetrator would most likely do anyway.
Also, the massive barrage of calls to her bf after the accident seem like an overkill (oops) if it was just to set up a scenario. I'd lean toward the assumption that at this point the phone was indeed in her possession and it was she who made the calls.
But then again, it's all assumptions anyway. :sigh: