Stepmom

"Still, the art of a movie like this is to conceal the obvious. When the levers and the pulleys of the plot are concealed by good writing and acting, we get great entertainments like Terms of Endearment. When they're fairly well masked, we get sincere films like One True Thing. When every prop and device is displayed in the lobby on our way into the theater, we get Chris Columbus' Stepmom."

—Roger Ebert's review.

A 1998 film, directed by Chris Columbus and starring Susan Sarandon, Julia Roberts, Ed Harris, and Jena Malone. Jackie and Luke are a divorced couple, struggling to help their kids Anna and Ben adapt to the new lifestyle as a result. Luke gets a new girlfriend in Isabel, a very successful advertising director who treats her career as the most important part of her life. Anna hates her at first, but after Jackie is diagnosed with cancer and starts treating Isabel better, Anna warms up to her. Isabel, as a result, starts becoming less career driven and more family focused.

The film represents sort of the logical conclusion of the Chick Flick genre taken to its extreme (think of it as the feminine equivalent of Last Action Hero, but without being an explicit parody). Formulaic to the core and 90% predictable to a fault, the 10% consists of either Dead Horse Tropes played totally and unexpectedly straight or just flat out bizarre Narm. The film often gets cited on how not to do a Chick Flick. Still, for those not too discriminating, it's fairly well made and delivers on its concept.

Tropes used in Stepmom include:

Actor Allusion: A snippet of dialogue almost certainly written after Julia Roberts was cast:

Ben Harrison: Do you think Isabel's pretty?
Jackie Harrison: Sure... if you like big teeth.

Soap Opera Disease: Jackie's "terminal" cancer. (And she's still alive at the end of the film!)
Will They or Won't They?: A non-romantic version, as the two main females have opinions that change so often in the course of the movie that the movie might have changed writers every five minutes.