The medical expense tax credit is a non-refundable tax credit, meaning that you will only get it if you have taxes owing. It will not generate or increase a refund. So yes, your mother can claim her medical expenses, but it will not make a difference on her tax return if she doesn’t need the credit to reduce the amount she has to pay in taxes.
This Canada Revenue Agency (CRA) page has more information on Medical Expenses: Medical Expenses 2021
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