Violet and the Pie of Life

There's no golden ratio for a family, despite what number-crunching Violet might think.
Twelve-year-old Violet has two great loves in her life: math and pie. And she loves her parents, even though her mom never stops nagging and her dad can be unreliable. Mom plus Dad doesn't equal perfection. Still, Violet knows her parents could solve their problems if they just applied simple math.
#1: Adjust the ratio of Mom's nagging to her compliments.
#2: Multiply Dad's funny stories by a factor of three.
#3: Add in romantic stuff wherever possible.
But when her dad walks out, Violet realizes that the odds do not look good. Why can't her parents get along like popular, perfect Ally's parents? Would it be better to have no dad at all, like her best friend, McKenzie? Violet is considering the data when she and Ally get cast in the school play, and McKenzie doesn't--a probability that Violet never calculated. Maybe friendship and family have more variables than she thought.