About 9 years ago my father divorced my mother and entered a sham marriage to obtain his residency. There was money exchanged and everything went through without problem, later he divorced the lady he married and later he got his u.s. citizenship. A few years later he got back with my mother who was facing deportation, around the end of 2010 she got deported. My father immediately started the process to bring her back legally and she finally got her residency after 2 and a half years of waiting. Now they are having marital problems and my mom wants to divorce him and get her permanent residency on her own but he is saying that if she does that then he will reveal to immigration that he setup a sham marriage in order to receive his residency, my question is would this have any effect on my mother's legal status after she files for divorce?