Hello,
The total income of your mother would be below the basic exemption limit applicable to a senior citizen assessee. Hence no tax would be payable.
Further investment in SCSS A/c. is eligible for deduction u/s. 80C. Interest from such A/c. is taxable but a senior citizen can claim deduction u/s. 80TTB for the maximum up to Rs 50,000 in a single financial year.
If TDS is deducted by the bank/post office on the interest, the income tax return of your mother can be filed to claim the refund.
I hope that this answer satisfies your requirements.
Regards,
CA Hunny Badlani