Yes, exactly. The people they stole from were either repaid with borrowed money (and when they defaulted on the loan, their house was repossessed) or never pressed charges and are now dead, their bank accounts wound up etc. One of the nieces who spoke on the podcast said she’d phoned around a couple of police stations, but that no one was interested, presumably because there are no living victims and the sole evidence of those thefts is family memories and a typed, undated confession letter Sally Walker says she didn’t write.
Someone like Bill Cole, the landlord of the cider farm they left abruptly having not paid the utility bills and without ever, in five years, making the cider their contract required, would definitely have a case for unpaid utilities and breach of contract (he is reported on the podcast as saying they’d cost him tens of thousands in lost earnings), but sounds too bewildered and hurt by it all to want to press charges.
And faking a serious illness in itself is not a crime. Nor is lying in your ‘memoir’. If, as we assume, Sally Walker signed the standard memoir contract, that contract will have stipulated that the book is substantially true to the best of her recollection, other than some identifying details changed for privacy reasons, so she will have breached that contract. But as the book was a huge bestseller, and made them lots of money, her publisher has no reason to bring a legal case, especially as it would only draw more attention to their lack of due diligence in fact checking.