Parents harrasing

My mother in law is harassing me and my husband by defaming us in our office and demanding for a very high maintenance amount. We got married 1 year back and my mother in law started to fight with my husband in a very bad manner about me. The whole family tried to pursue her to not make nuisance in the house but she has not changed and increased the level of fight. She has also threatened me to murder me in one of the fight. Still my husband tried hard to to ask for peace but in January, we decided to stay separately from her. My husband is paying the EMI of a flat which is jointly hold by her and my husband. She has not paid a single rupee for the house but threatened us that she will take over the house and will not let us sell the home. She is now also demanding a huge sum (50000 minimum) as her maintenance and threatning us to go in court against us. The major concern is that she is calling in my husband's office to different people and defaming him and putting allegations on him. Please suggest what actions we can take? Also what is the optimum maintenance amount she is eligible of?