Divorce notice given by daughter in law

My cousin brother got married around 5 years back and now has a kid with his wife. Post marriage the wife had moved in with my aunt and uncle as my cousin works abroad for 8 months and then comes on vacation for 3 months. After a few months she started getting into heated arguments with my uncle and aunt and started complaining to my brother. Eventually my brother moved her out into a separate apartment in the same building where her parents stay. My cousin regularly sends money for all household expenses and the child's education. This year when he came back she not only refused to take him into the house or let him see the kid, she even beat him up and threatened him with police complaint for harassment. She is not in touch with anybody from my brother's family. But now she sent a divorce notice with multiple harassment points ranging from how my uncle and aunt beat her up, asked her to do household work, asked for dowry of 10 lakhs, were abusive to her. She has even blamed my uncle who is a senior citizen of sexually assaulting her and that my brother has raped her before marriage. We come from a highly educated family and these things are next to impossible to happen in our house. Most of her claims are baseless and not true and she has included everything possible just to keep the child custody and get a hefty alimony. What is the remedy against such false accusations. Both my uncle and aunt are very decent people and are very worried about their reputation getting destroyed in old age.