It seems like for the "mastermind theory", the last thing one would ever want to do is bring someone into the fold who would stay behind and knowingly shoulder all the legal trouble. And from her perspective, getting married and being named executor would be a terrible idea drastically increasing her involvement - an unmarried "girlfriend" could passively walk away while the legal system did its thing.
If this was an exit scam, it seems highly likely that Robertson was an unwitting patsy. Granted, encouraging this conclusion is a large part of why she'd write a book. But I just don't see how the alternative would make sense in the slightest.
I get the sense from the various posts and book excerpts and her podcast appearance that she isn't the sharpest tool in the shed nor a criminal mastermind, so to speak.