Leave Her to Heaven (1945)

Novelist Richard and Ellen get together almost immediately after meeting on a train. Her family seems to characterize her more reckless decisions as normal for her -- a sign of free-spirited fearlessness -- and Ellen's mother even tells Richard that Ellen loves too hard. But they marry and Ellen throws herself into domestication. It's only when Ellen's family comes to visit that Richard seems to notice Ellen's mask slipping a bit, while mother and sister recognize her impatience and rudeness as Ellen being Ellen.

Long story short: things go very badly and I think undiagnosed Borderline Personality Disorder is to blame. Gene Tierney is both gorgeous and chilling as the calculating Ellen.

B