Deceased brother's wife claim for theft of PLI from their house

Hi, I lost my younger brother due to heart attack in Hyderabad. He was married to Kerala lady in 2021 who is Christian (love marriage) after spending live in for 2 years. After completion of ritual at Punjab myself with my brother in law, his wife & his wife's brother went to his flat to apply for death certificate. His wife left to home town in mid of the process. Later on she complained that we theft postal life insurance (purchased by my brother) from her flat in which my mother was nominee. She came to know about this once we applied for the claim in Haryana. Actually PLI was kept in Punjab only. Now she is also claiming 50% of the claim amount. Even she withdrawal 2 lacs from my brother account after his death. She also kept custody of his mobile, email & all of the documents. We are totally blank about his investments, real estate property etc. His wife have gynaecological problem and was unable to give birth. They were trying IVF but she is also not telling about anything whether it was successful treatment or not. I lost my father when my brother was 15 years old and I took charge for all our family needs of 5 members, education of brother & sister, both sister marriages & my marriage. Even my brother preparation for Job was done when he will living with us in outside town where I was doing job. Please help how I can fight this matter.