My mind went to the possibility of a drug-related death (possibly OD, but not necessarily) because of PH's history of addiction. IMO, that adds a whole other level of risk - the lure of the drug itself, plus the circle of people involved - not users so much as dealers experienced in hiding illegal activity. It seems reasonable that she saw someone familiar at the bar and willingly went with them, thinking she could "handle her own self" and spend some time with some of the "old gang" without getting in too deep. Over the next hour and a half, it's possible the places and people around her changed a few times - rides here, dropped off there, a constant flux until PH starts to realize she's no longer with anyone familiar, and maybe "in trouble" because she's not sure she can (1) resist the urge to use, and/or (2) get away if/when she needs to.
If she did, in fact, leave her co-worker(s) at the bar, I don't feel it was up to them to "let" her go or stop her from it, or to track her down via texts or phone. And, after being left at the bar, it seems logical to me that the co-worker wouldn't stay around, but would go home and go to sleep. I can also easily imagine how to some extent her story may have changed, if it did. Waking up to that text, not being able to reach PH, and then speaking to her family in a panic vs. taking time to concentrate & and pull every detail out of your memory? Could certainly result in correction of certain details, descriptions, etc. Of course, major contradictions would raise suspicions, but there's been no reporting of that that I'm aware of.
It seems LE fairly quickly either figured out who the "two guys" were OR determined there were no such guys, based on the fact that they (as far as I can tell) didn't continue to ask the public for help in identifying them. It also seems like the co-worker(s) would've been named POI by now if she/they were directly involved - but maybe that's an unrealistic expectation? Either way, I think co-worker was right not to attend the yellow-ribbon event. If the family has indicated publicly that they, to any extent, suspect or blame her, showing up would have been very disruptive and disrespectful, IMO, even if she (co-worker) is 100% blameless.
This is just where my thoughts have ended up after the last several days.