Is there anything I can do?I cannot figure her out.?

I simply cannot understand what she is doing.My daughter lived with us for 3 years after she left her boyfriend.She also has a son who is 5 and he has been cared for by my wife and I pretty much since he was a baby.This all started when she met a new guy,who by the way lied about being married ,his age and the fact he has a sexual dease.She has now moved out and decided that my wife can no longer that care of our grandson.This is I assume because we will not accept the new boyfriend.My grandson is heartbroken and she does not seem to even care.She has never been a real mother to him and I don't think she knows how.She doesn't have the I will do anything to make sure my son is safe and happy.She seems to only care about what she wants and does not care who she hurts or what she has to do to get it.Help,I am hoping maybe someone will have a suggestion,anything.Any thoughts would be greatly appriceated.