She KNOWS you care. That's why she's got you right where she wants you. She also knows that you and your husband are GOOD, decent people. She uses that against you also because goodness has rules of conduct...like tolerance, patience and doing CERTAIN (rules) things within the parameters of decency and kindness.
Yes, yes, she's got you wrapped around her finger.
My mother (and sister, they were a team) was like that. I am the most principled person in the family (this disturbs their conscience). This is why your mother will not leave you be,...because you and your husband have always disturbed her conscience. Whenever somebody senses a lack of insecurities in another person (in other words, they see the other person has a clear conscience because they are principled, they start to feel uncomfortable and think that the other person might be better than them.
Your mother resents your nobility and kindness (it makes her look bad, she is the parent and she is supposed to be superior in every way (HER POINT OF VIEW). This is why you will remain her enemy and she will NOT change.
NEVER sign anything (it makes you legally responsible, that is why she wants you to sign). Don't think she won't use the legal system against you. After you evict her, watch her as she leaves so she doesn't leave a lit match in a couch or leave a 5 thousand dollar charge on your phone bill, etc. You are not dealing with a good or reasonable person. According to her way of thinking, she feels justified in anything she wishes to do, she feels that she can do no wrong that is TRULY wrong...she feels that whatever she does is only SNEAKY or NAUGHTY. In other words, she THINKS DIFFERENTLY, don't underestimate her conniving schemes.
Don't feel guilty or ashamed for showing her goodness and kindness (in my opinion, it's been more than she deserves).
Something happens to people when they get older and have underlings (especially if the older person is not independent). Their ego makes them ashamed to depend on the underling for even a smile (you are an offense to her ego). You have treated her well and, instead of responding in kind, she provides you with misery (you are an offense to her conscience also).
She is and always will be frustrated that you won't allow her to have possessive control of you and your life. Be aware that she might go to the police and badmouth you behind your back or do something behind your back to cause trouble for you in some way. You are a target because of her insecury about herself.
and you think she's going to change?
(oh, did I neglect to say something good about the kind of person you're dealing with?). We continue to love our parents no matter what because we have love in our heart (in some strange way, they do too), but now their way (for some)of thinking has become adversarial.