Death of husband-mother in law is asking terminal benefit share

Dear All, we were 4 family members in my family, myself, my husband, my mother in law and my husband who was working in private bank and passed away few months back. Bank has forwarded me the claim documents with indemnity letter to be signed by mother in law declaring that she is having no objection to transfer death terminal benefits to nominee i.e. myself. After one month me and my mother in law mutually decided to separate and afterwards she went to bank and said she has not given any indemnity and asking her share of death benefit. I am having one year old child responsibly on myself and now bank is asking to submit the succession certificate. Need your guidance please.