Those are all fact-specific questions and the legal issues have to be sorted out before the tax answer can be found.  Did the creditor ever try to collect the debt from her? Are they still trying?  Maybe they haven't sent her a 1099-C yet because they think they can still collect it from her.  

A canceled debt is still taxable even though no 1099-C is issued.  A canceled debt may not be taxable even if a 1099-C is issued.  Focus on what happened, not on the piece of paper.  

And as I am reminding a probate client, the issuance of a 1099-C is not a defense if the bank decides to sue the estate (or its beneficiaries) for it anyway.