If she lives in a province that has a rent credit, then yes you can.
Ontario
Where about do you claim that?
It had mentioned in the trillium section but says can't claim that if passed
You can find the rent credit as part of the Ontario Trillium Benefit in the Provincial section.
Unfortunately, your mother in law doesn't qualify for the 2024 Ontario Trillium Benefit.
Thank you for the replies yes I was kind of thinking it was in the Trillium and her not being eligible thanks for the confirmation.