One would think so, but meth freaks who traffic women and carry guns and chains are not logical or rational types.
Once they made their 'mistake' they had to figure out the next step. Just letting her go immediately is a big risk. So they probably tried to find a way to still sell her to someone, somewhere. That took awhile. It apparently didn't work.
They probably considered killing her, a few times at least. At some point, ONE of the women decided to take her for a ride and set her free. It might have been an impulsive decision.
Still think this scenario makes the most sense. Two women involved in the drug trade or something similar, travelling along the I-5 corridor, the Papini's (old) home is a hop skip and jump from that corridor, the 2 take a brief detour from the 5 or are more purposefully right in SP's area, they see a very young looking very white woman all by herself, no one else on sight, they snatch her, with vague plans of selling her to folks they know are in that trade.
But, they find out fairly quickly she's married (wedding ring) and she tells them she has kids. Not what they were thinking, ups the risk, but they've already kidnapped her, and things can still work out.
But, the publicity comes quickly and becomes increasingly intensive. Their associates don't want any part of it unless the PR settles down, but it doesn't. They're stuck with her. Then the ransom becomes an open invitation for bounty hunters to start searching, or anyone else who might have seen them or who knows them to snitch, and they need to end the limbo. One wants to kill her, the other releases her.
Yah, speculation, but yah, stranger things have happened.