Should siblings Contribute Towards Rent?

My husband and I renovated a flat on our property for my widowed mother who earns very little by way of a pension fund and the day she moved in her car was stolen. The idea of her staying with us was lovely because she was independent, but wham! She moved in and became our sole responsibility - everything from her shopping to social visits and entertainment has now fallen on our shoulders.

We never asked the family to contribute to the renovation or to her living expenses, but now three years later I have had enough of their lack of involvement. We had a family meeting to discuss contributions towards our mom staying in the flat to defray some of the expenses but it turned out really bad! We were accused of being uncharitable and using our mother as a pawn to make rent money.

According to them we must see her as part of our family and we need to make monetary sacrifices as we would do for our own kids. We were made to feel like we were money grabbers!

Are we? Is it wrong to ask for rent or monetary contributions to the expenses incurred by an extra person living in our home?
Please help!