Sounds like nonsense to me. The will may have been made back in 1985, but until the property actually transfers ownership then as I understand it it is what is technically called a "non-vested contingent interest". In other words, it doesn't "vest" in a trustee in a bankruptcy (or convey to a trustee in a Protected Trust Deed) unless the person dies prior to the debtor's discharge.
So as long as your mother-in-law was discharged prior to her mother dying then the trustee should not have any claim over it.
I believe the Accountant in Bankruptcy lost a case in court recently whereby they sought to gather in a life insurance payout when someone's spouse died just after that person had been discharged from a bankruptcy. The Sheriff ruled that a life insurance policy was a non-vested contingent interest and would only be able to be gathered in by the Trustee if the spouse had died prior to the debtor's discharge. I don't see how this is any different.