Could she not have her own place and live there when the kids are not around? I completely understand your need to be alone and though it's good of her to help, it's not ok for you to give up your personal space entirely, in my opinion.

My sibling wants me to live near her, but I already feel crowded living in the same town. Even though it hurts her, I keep telling her that I love her, but hell will freeze over before I even so much as move to the same district as her.