I haven't found any cases of blonde joggers of any age abducted in the US by sex traffickers. What would make sense if the high profile aspect got to them would be to kill her and hide her body. Of course someone might find a remote case somewhere, but add to it that she was released....even more rare. JMO
Sounds like only one of her abductors actually released SP. Maybe the other one wanted to kill her.
We're talking about folks who were willing and able to snatch someone off the street, then to brutally torture her for weeks. That's not plain vanilla criminal behavior, and imo it suggests these folks were capable of killing SP but didn't.
Since all we can do is guess, my guess is that things didn't go as originally planned, for multiple reasons, including the intense state-wide then national publicity about SP's abduction. There was nothing inevitable or predictable about that degree of publicity, especially if her abductors had no idea who SP was.
If so, I think it's possible the person who released SP did do because her other captor had decided the only way out of their FUBAR was to kill SP, and SP's releasor either didn't want that to happen or was afraid at that point they were going to be caught.
Just speculation, obviously.