Would you charge a family member 'rent' under these circumstances?

You call your younger sister and tell her that Mother is going through chemo and possibly dying and that she should come home and spend some time and help. Your younger sister has no children, but in order for her to come ‘home’ she would need to quit her job and leave her husband for a time to pay for the mortgage on his own. She does this, but then when she asks to stay with you while she helps out, you ask her to pay you rent.