I've bounced in and out of this thread over the past couple of weeks so my apologies if this has already been discussed.
Could it be possible that Paighton came across someone at the bar she knew from rehab? Then they went off with, perhaps, people known to the friend? That would explain why she left initially, a relapse, let's go party, and the text saying she didn't know where she was or who she was with and that she might be in trouble. I think the "trouble" comment was meant to mean drugs.
I am going to stick my neck out and suggest, if this is Paighton, that the cause of death is going to be an accidental overdose.
For those that may not know, many addicts overdose accidentally after being sober because they shoot up with the same dose that they were accustomed to using at the time they stopped. Since they've been clean, their body can no longer tolerate that dose. Prior to rehab they were building up a tolerance bit by bit and increasing their dosing bit by bit. To be clean and sober and then go right back to the highest dose you were taking before you got sober is a recipe for a fatal overdose. (Corey Monteith)
Just throwing this out there. I could be entirely wrong. It's going to be terribly sad no matter what the COD.
MOO