How can I ask my mother-in-law to move back to her house 6 months after my father-in-law passed away?

My father-in-law passed away six months ago at their home and my husband and I invited my mother-in-law to stay with us so that she wouldn't be alone. We never discussed whether or not this arrangement was permanent. We have two children and we really don't have the space. How do I respect my mother-in-law, who really is great, while expressing that we really need our space and privacy. My husband seems somewhat content with the arrangement, but she makes me crazy! How do I get my home back without disrupting family harmony?