The mother may be having plenty of reasons to justify the expenses out of the insurance claim amount or any other amount received as terminal benefits of her deceased son, but as per law, the widow is also one of the class I legal heirs and her marriage subsisted till the time of his death, hence a widow and one of the legal heirs of the deceased she has an equal share in all the properties left behind by the deceased.
The nominee for insurance claim amount shall receive the amount on behalf of the legal heirs as a trust an then disburse the same equally among all the legal heirs of the deceased, hence she cannot claim the entire amount for herself just because she was a nominee.
As far as the EMI for his property under loan, this property also to be divided and distributed among the legal heirs equally.
She canot claim absolute ownership of this property ignoring the widow of the deceased.