If she is elderly, it could be aging... thriftiness and fear of not having enough money... and being set in your own ways (having lived alone for a long time) makes change hard and uncomfortable. Maybe she agreed to rent out because of money issues, or family urging her and she really doesn't want to?

She doesn't sound dangerous. Be nice. See if you can have one more adult conversation and agree to write things down (two copies) so she can remember what you agree upon... but in the meanwhile look for another place...I doubt she can change.