In relation to whether the mortgage is a charge on the residue …
Liabilities connected with non-residuary gifts are only deductible as a charge on the residue if they fall exclusively or primarily on the residue.
Mary inherited the property as a specific disposition and as a non-residuary beneficiary. The mortgage is, therefore, not a charge on the residue.
If instead, she had inherited the residue including the property, then the mortgage would be deductible from the residue – TCA 1997 s 799.