I agree completely with your assessment of MoM, Judy. It indeed fails to establish enough of a reason for Margaret to go off the rails to such an extent. And she's such a nut from the very beginning! I like the movie, but I feel like it doesn't quite get where it wanted to go. And the writer/director tries to marry the style of screwball comedies of the 1930s with an adaptation of the novel Rameau's Niece. It's not an entirely happy marriage to my way of thinking.