My mother owns a home, has moved in with me as she is unable to financially or physically maintain her property. Her sister is living in my mother's home, has been there about 3 years, only the last 3 months without my mother. She is just paying the utilities (her own usage) and no rent, or anything else. We just requested that she move out by January 31, 2012 as the house is being listed and we want it vacant at that time. She says she can't be 'evicted' in the wintertime. There is no rental agreement as it was a verbal agreement that she could live there and pay the household bills until the property sold. Given her uncooperative nature, we want her out for when the property is listed. The home is in Ontario. Does she have any tenant or other rights here?

No, but you do have to evict her formally through the courts if she fails to leave.
You might want to list it with her in it for a few months anyway, because someone will have to keep it heated and lit if it's for sale. And not many sales happen in the winter. You could perhaps write a contract until March 1 in which she has to pack most of her possessions and keep them neatly in one room, and be ready to move after the house is sold, since closings take some weeks. You don't say how nice or awful the place looks with her there. Empty houses also don't sell as well as furnished ones.

Oh, and of course it's your mother who has to evict her. Maybe she should give you some Power of Attorney.

Joy is right, an occupied house will sell faster. But there is no law that someone can't be evicted in the winter.

Agree, you will have to evict though the courts. And why not charge her rent if she is living there ?