I don't mind Margaret. Yes, she was really annoying at the end of season 2, but her daughter had polio, I think she kinda had a right to go crazy, she also embodies the morality of the show. She thinks bad things have happened to her because she has been a part of Nucky's "evil" ways of doing business.
She thinks life is trying to send her a message, which had a part in her going crazy as well. And like most mob movie wives, she's beginning to ignore them because Nucky brings home the bacon.
I'm wondering if she will leave him at a certain point, but how could she? Since she needs her kids to be provided for, and its not easy providing as a single mother in the 20s.