I'm starting to consider that perhaps SL's job as a cashier at Menards may have made her a target. The judge used the word "parallel" and to me, this suggests there is something similar, or somewhat connected to their charges of theft.
I'm thinking that BB and AT may have been very interested in the dozens or perhaps even hundreds of credit card numbers/transactions that SL would have handled during each shift at Menard's. Their previous thefts required they face their victims and this is what got them caught as they were identified by their victims. But with credit card numbers, there are so many possibilities of stealing money without having to face the person you are stealing from. For one, they could sell this information to other thieves, or they could make fake credit cards with real numbers and sell those.
It is possible that BB thought she had totally charmed SL on their first date and that she could easily talk SL into going along with their plan. I think SL was looking for love and when the theft proposition was made to her, perhaps on the second date at the apartment in Wilber, she became very upset by being duped, and realized that BB's only interest was to try to use her.
Things could have gotten out of control with SL being very upset. It could also be as simple as AT and BB fearing SL was too big a liability to let her go as they feared she could go to the police and she could identify them, tell them where they lived, etc.
I don't know what happened, but this doesn't seem implausible to me. The fact that BB is using a public defender tells me she is indigent. AT will not hire an attorney and insists on representing himself. He may not be able to afford an attorney and his ego will not allow him to use a public defender.
In any event, I do believe that both AT and BB were in pretty desperate circumstances at the time they met SL and desperate people can do desperate things.