I also, less famously, dislike Joan Fontaine. She's a wispy, feckless thing on screen whose posture is atrocious. My sister, incidentally, does a great imitation of Joan Fontaine as Peggy, the ingenue you want to smack, in The Women. Maybe I'll record her doing it and post it some day.
DeHavilland's Terry — much like the character she played two years later in the excellent Snake Pit, Virginia Cunningham — is a person with actual psychological problems caused or exacerbated by some very real conditions like depression, trauma, or plain old mental illness. Terry's anger and contempt are spectacular, while her easily-driven-crazy twin's bewilderment is just annoying.
As a rule, watching a girl being driven mad is kind of a bore. I mean, really, if you hear a music box playing somewhere in the house, chances are your twin sister left it in a drawer someplace and you're not really hallucinating. And if she tries to convince you some morning that you woke up screaming in the middle of the night confessing guilt for murdering someone, she's probably just messing with you. Seriously — Occam's Razor.
I've seen this movie a number of times, though never on a big screen until last night at Noir City 9, and I never remember that Thomas Mitchell (Uncle Billy from It's a Wonderful Life, Scarlett's father in Gone With the Wind, and Dizz from Mr. Smith Goes to Washington among 50 million other pictures) is in it as the police lieutenant and that he's great. Just great. A couple of his best lines:
** "He's a pretty smart guy for a college man."
** "Even a nut will figure out that it's easier to kill a rival than than to knock off her boyfriends for the rest of her life." (or something like that. I was very tired.)
Please do see it if you can. It's not on DVD, but you could probably find it on a dusty old VHS someplace.