Regarding Divorce

My brother got married with a girl on 27th May 2023 but after 2-3 days of marriage we got to know that she is not normal, her behavior is very strange, after 10-12 days of marriage their family members come and take her with them and whenever she comes she lives here for few days and after few days her family bring back her with them, during living here, she reveals herself about her medical conditions that she lives in metal hospital for 2 months for 2 times and she run away with 4 different boys for 4 times before marriage and done sex also, she also told her that she is getting angry when kids in our family plays at home, she thought to hit them. She also told us that she hit herself once with a hammer, we have all these things in video recording also and some of the things written in paper by her. Now the question is that her family is denying of her mental illness and neither they are providing any medical documents, how to get divorce from her and how we can save us from any law as they are completely wrong in our case