Worded incorrectly. I was trying to refer to cost sharing vs rental income. If you are going below fair market you have no intentions of turning a profit there for you are cost sharing. So just rent the room for under FMV and you are fine she isn't entitled to your property and you don't need to claim anything.
"Renting below fair market value You can deduct your expenses only if you incur them to earn income. In certain cases, you may ask your son or daughter, or another relative living with you, to pay a small amount for the upkeep of your house or to cover the cost of groceries. You do not report this amount in your income, and you cannot claim rental expenses. This is, in fact, a cost-sharing arrangement, so you cannot claim a rental loss. If you lose money because you are renting a property to a relative for a lower rate than you would rent it to other tenants, you cannot claim a rental loss. When your rental expenses are consistently more than your rental income, you may not be allowed to claim a rental loss because your rental operation is not considered to be a source of income. However, you can claim a rental loss if you are renting the property to a relative for the same rate as you would charge other tenants and you reasonably expect to make a profit. "
http://www.cra-arc.gc.ca/E/pub/tg/t4036/t4036-12e.pdf