بسم الله الرحمن الرحيم
(Fatwa: 1263/1181/SN=11/1438)
If your grandmother is poor and destitute then you may give her interest money but it is better if you support her with your halal income and give the interest money to other poor and needy people.
Allah knows Best!
Darul Ifta,
Darul Uloom Deoband
