Mother taken advantage by one of the married daughter

It's been 7 years (father passed away on april 2010) that our mother is taken advantage by my second sister (married). We are turning 32, 31 and 30 years old now (3 unmarried daughters). After my father's death, she got very close to my mom and 2 of my unmarried sisters and built them against my elder brother who used to take care of finances. She started interfering in family related finances - took certain portion of income in the name of my mom with the help of my uncle (father's brother) and family friends.My worry is not that i am still unmarried, nor that i am unable to tell my mom and my other sisters of their mistakes. Am doing all that's under sky to do so. I need help of law to worn my second sister of her motives and her conduct since our father passed to even today - make my unmarried sisters to baby sit her son and evrtym take my mom along as she if she's the only one who loves her. I have my uncle, aunt, elder brother, first sister, brother-in-law, cousins, friends suppo