It is my understanding that Mariah tried several times to help her sister get her life sorted--including paying for rehabs. It is down to Mariah and Nick who they want in their children's lives. Addicts are notorious for coming out crying if they think they can shame a dime out of someone. It's a shame that this is the state of their relationship, but I can understand if Mariah decided that enough is enough. I'm not a Mariah fan, but have had addicts/alcoholics in my family, so I've seen this behavior.