Cruel Nature of Sister in Law and threats from her family

Hello, My sister in law is from Batala, Gurdaspur (Near Amritsar). In her family, there is one brother and her mother only.We found her profile from a matrimonial website. My eldest brother just met her once for first time in Amritsar in August last year, and the marriage was decided on 5th October. On 31st September, our family went to Batala for Roka Ceremony with only 15 people from our side. After this, we requested their family for marriage to be done in Delhi (from our side), but they refused, and we 9 people from our side went to Batala for marriage. Now, since second week only after their marriage, after returning from her honeymoon, my sister in law started showing her rude nature. She started blaming my brother for having contacts with girlfriends, and, etc. But everytime she created some nuisance , the next day she again starts behaving nicely like a kid. But this continued every week. She started blaming my mother that she brain washes my brother, so that their relationship could worsen. Everytime after some dispute, she started calling all her family members, that we are beating her, we are torturing her and she is being mentally harassed. Her family members never talked to us, and everytime we tried to tell them the reality, they continued blaming us and threaten our family that they will harm our mother and will go to my brother`s office. My sister in law and her family threatened us that they have strong contacts in Punjab Police and will get us caught , if we say anything to her.Our mother, requested in a neighbouring playway school for a job for her. So he joined there in march. Her rudeness continued but in March end, one day again on some non-sense topic, she started fighting, and went down on the street and gathered all neighbours that we are beating her and asking for dowry. She started calling her family and told them that my mother is hitting her and i am trying to molest her. The same day her brother called our local police station and complained that we are doing domestic violence and police came, they asked her to do medical test but she disagreed for doing so and said i will take care of this. the next day my brother and sister in law seperated in other house but her cruel nature still resided, she could not bear my brother coming to meet us and our mother. In April end, one day she went missing when my brother was in office, we tried calling all her family members but no one picked up, so we filed missing complaint but after 20 days my brother receives a call from my sister in law that she is at her home. On 14 June, we receive a call from someone who says he is Court Reader from Gurdaspur court and says that my sister in law has filed dowry and other allegations on our family, my brother asked for summon or any notice but he refused and said that my brother needs to come and give statement on 5th July. We didn`t go there as everyone told that we should not go without any summon or notice.What should we do now?