In The Great Gatsby, Daisy tells Nick that she hopes her daughter will grow up to be a beautiful fool:
...I hope she'll be a fool--that's the best thing a girl can be in this world, a beautiful little fool.
I interpret this statement to be satirical and ironical on Daisy's part. Daisy is intelligent and is capable of satire and irony. Daisy knows this is the way for a woman to be successful and upwardly mobile in her society. It's what Daisy has had to do. It is easy for readers to condemn Daisy, but a reader's first duty is to understand a character. That's one of the things mature, sophisticated fiction is about. And a woman in Daisy's world has limited options. That has maybe changed today, but it took many decades since the twenties to do so. Daisy is commenting on her society and the predicament a woman faces. Being a "beautiful fool," or at least playing the role of a beautiful fool, is the daughter's only hope, in Daisy's eyes. She will have to play along with men as Daisy has had to play along with her husband.
You can find the answer to this in the first chapter of the book.
Daisy tells Nick that she hopes that her daughter will turn into a fool. Specifically, she says that she hopes her daughter will turn into a fool who is also beautiful. She says that that is the best possible thing for a woman in their world to be.
In my opinion, this shows that Daisy is not happy with her life -- with her marriage in particular. I think this is because she knows that Tom is cheating on her but yet she can't really do anything about it. If she were stupid, she wouldn't know anything was wrong with her marriage and would be happier.