So every time the Wind blows, Diane goes a little crazy. She enters a sort of fugue state, and does things she can't remember. Like kill Christie's friends, her horse, and freak out a little that she can hear her baby crying in the distance.
Ultimately, we learn the reason Diane's so screwed up, and Edna's so mean. By the time we get this information, though, I had a really hard time caring. I just wanted a house to fall on them both and be done with it.