The Private Lives of Pippa Lee (2009) on Netflix

At fifty, Pippa Lee positively glows with female serenity, the devoted wife of a brilliant publisher thirty years her senior, proud mother of successful twins and a lovely and adored friend and neighbor. But, when her husband spontaneously decides that they should leave New York for a retirement home as a "pre-emptive strike against decrepitude," and has an affair with someone even younger than she is, Pippa finds her beatific persona unraveling in alarming ways. The truth is, the gracious woman of the present day has seen more than her fair share of the wild side. She has finally found love and security in a family of her own. And now, that cozy world, too, is in danger.