This going to sound REALLY cruel, but Barb may have to throw Chris under the bus.
If she implies that she was aware of what's going on and allowed it to continue, she could be facing a Class 5 Felony herself. And if the both of them go to jail, even if only for a year, they won't have a home to go back to. The bank would easily seize on the opportunity (and the subsequent lack of payments) and take everything.
If she plays incompetent (or is actually incompetent, make your own jokes here,) she would at least be deemed an innocent victim and allowed to return home. Unfortunately, unless Chris put her in charge of collecting tugboat, Chris' absence would mean a drop in household earnings, and that household can't take anymore financial worries as it is. On a side note: that house is also dangerous, and as laughable as it sounds, Chris not being there means that an old woman is navigating through a cluttered dwelling that's also a huge fire hazard. I fear that unless a caretaker is issued or she gets put into a home, that her life would be in constant danger to the point where it's not only a matter of 'if' something falls on Barb and traps her, but 'when.'
On the topic of Chris defending himself in court: Man, would that be a sight to see. But believe it or not, such a thing might actually help him, if only for the reason that it'll definitely prove that he's crazy enough to be put into a mental institution as opposed to a prison. Unfortunately, if Chris does lawyer up, it's going to be a State-issued one. No Rob Bell to save his ass this time. Chris is at least autistic enough to read some rehearsed dialogue, but it'll all go to shit once the recordings get submitted as evidence, upon which, he'll end up spilling everything and sing like a canary or attempt to commit perjury in court.
The question of what Barb is willing to risk depends entirely on her mental state and how much she actually cares about Chris, or, conversely, how useful she thinks he is anymore.
There's a saying that goes that "All mothers love their sons," but if Barb was an manipulative as many people say, she may weigh these factors out to see which is more favorable for her, rather than Chris. And I ain't gonna blame her, I mean, after all, Chris DID rape her.