Sister in Laws

Hi, I have a sister in-law from "HELL". She treats my brother like crap and all of his family. She threatens him with divorce all the time. My brother own his own business and she hates everyone my brother hires to mandate the front office. Anyway, my brothers business was in the dumps the IRS was getting ready to shut the business down for non-payment of taxes. My brother was in such a financial mess. He spoke to our younger sister who was unemployed at the time and she agreed to assist him get his business back on track. After five months our younger sister had organized the office, cleaned up all the IRS issues and business was booming. They (brother and sister) found that his wife (sister in-law from hell) was emblezzling money from the business and she refused to stop writing checks from the business account. She told my brother that he would have to chose his sister or her and their kids. My brother is so scared of her (if you see her you would see why she is UGLY). My brother asked our sister not to show up at the office his per his wives orders. She threatens him and turns their children against him. She doesn't allow him to go around his family members. My sister inlaw has physically hit my sister kids because she is jeolouse of our family. Our mother is on a fixed income and if my brother even attempts to help my mother financially she (sister in-law) throws a fit and starts fighting with him.