It's a dangerous plot premise- already you've got the Mrs. Scott Fienstadt (Topher Grace), the same name as the young love of her life who died, comes along she has no problem going completely out of her comfort zone and daily routine to meet, seduce, and compare the new to the old, or rather her indestructible memory of the old.
She lives her safe and humdrum life working at Admissions for Columbia, talking to her best friend (Marcia Gay Harden) who is going through her own adulthood misery, and watching happier, younger couples from her office aloft. Basically the film is about a lonely 39 year old woman named Louise (Laura Linney) whose only friend (self-admitted) is her ex-husband.