My brother's wife is very toxic

Hello myself Rakhi. We were family of 4 myself mom dad and elder brother. 2 years ago my brother got married it was an love marriage my parents completely opposed it still we had to accept it based on my brother's stand saying girl is very good one, she had completely brainwashed him back then. After the marriage she was happy doing all the households Pooja on her own that too for 10 days that's the last few days of our life , suddenly she stopped doing any work started staying in her room when my brother asked her what's wrong she started behaving rudely my parents tried to resolve the matter by talking to her all they received was rude arrogant replies from her all this drama bcos she said she wanted to see her mother . We sent to her mom's place thinking all this outburst because she misses her mother but she gone for 1 nd half month didn't even tried to come back she won't even call until we try to reach her. Her family don't even own anything completely poor they can't even feed themselves for that also they call my brother demand money for taking care of themselves this all kept secret from my brother we got to know recently .after 1 and half month she came back and still acts like we are strangers to her she does her own things . She'll act nice when she needs something if we fail to fulfill that she shows her evil side talk rudely to my parents that too without any respect . We even tried bringing her mom which her only family member her mother all she did was put all blame on us saying we torturing her daughter which is completely opposite she created a big ruckus and left warning us. In all this we are the one who are suffering from her drama and she and her mom acts like it's all our fault . When she is conceived with baby we looked after her completely which is our and her mother's responsibility she showed no gratitude we didn't care either as she is our family member. She went to her mother's just on 9th month after baby shower in our home which is our tradition. After 3 weeks baby is born and we took care of everything hospital fee to all the expenses baby should stay in her mother's place until 9 months. For that also we paid them completely all she said was she can't look after babies and her expenses as they are very poor we did everything possibly can . After 9 months when the baby came here she was happy and different for 1 week like when she came after marriage. Again same drama ever since. Now from past few months all she says is she wants to go back to her mom's. She wants divorce. When my brother buys her nice things she acts nice for another few days . Again she repeats her drama. Everyone is tired of her drama we completely lost our peace of mind .we Love that baby so much we can't live without him but she is scaring us saying she'll take him away with her . We are suffering a lot bcos of her cruelty. Please help me out with suggestions what we can do . Please