Your landlord is such a piece of work. I would be willing to bet she's got someone behind the scenes telling her what to do, pulling the strings so to speak. A brother, uncle, mother, someone, possibly even a group of someones must be provoking her. I've found that to be true in a good majority of situations like these -- people fall victim to some sort of distorted groupthink and work themselves up into a frenzy of righteous indignation.
In China the law favors you as the tenant. It is very hard for a landlord to actually evict you (they can resort to thuggery, of course, but the police will generally not force people out of a home, at least according to my husband). Especially since, as you pointed out, you owe her back rent so she actually at this point stands to lose more than she would gain. So much BS.