This is owing, I should think, to her inability to understand that the world isn't made up of monsters like her and John. The same woman who fears Mira's generosity because she can't understand why someone would do things for someone without asking for something back can't or won't admit that not everyone wants to explode in rage at people who inconvenience them. The silent contempt of the man whose car she dinged is a baffling thing because she doesn't realize that she's not going to be the target of the man's rage. In her mind, it's far better to be screamed at and know where she stands than to endure a withering glare from someone who she'll never see again and only thinks of her as "some idiot woman I met once who can't drive."
What makes her moral cowardice even more entertaining is that when Mike panicks about the horrible prospect of his being teased because she wanted to wear Bermuda shorts, she deferred to him. That totally God-damned baffles me because I'd have been all "Shut the Foob up, you little communist. You're not the boss of me!" Instead of being a parent, she turned into an idiot pandering to the needs of a spoiled wad of crap who can't take teasing any more that she can take being lectured to.