That Scarlett transcends some gender roles is true; however, it was not unheard of that the matriarch of the family did much of the bookkeeping on the Southern plantations.  This occupation was very time-consuming; hence, the Mammy cared for the children.  That the wife of the plantation simply organized social events, and other frivolous activities is simply not true. The main difference between Scarlett and the other women of her times is her ignoring of the social mores; she does not disguise her intellectual abilities under a bonnet and behind a fluttering fan.

In the South during the Civil War, there was the perception that women belonged to men and needed to be taken care of.  There was also the perception that men should treat women in a certain way, with exaggerated courtesy and chivalry.  In time of war, sometimes social convention is not the most expedient.  Typical gender roles can fall by the wayside.

The book and the film are a bit different. In both, however, Scarlett, faced with extreme hardship, transcends expected gender roles for southern white women. She is a businesswoman, for example. Mitchell shows that, even from her youth, Scarlett always chafed at the constraints of gender in the plantation South, a fact that was dramatized when Mammy strained to squeeze her into her corset. In fact, early in the book, Mitchell says that Scarlett "wanted to be a man." By the end of the book, she is fulfilling masculine gender roles, serving as the head of the ruined Tara. Below is a link to a thought-provoking scholarly article on this very topic here on eNotes:

http://www.enotes.com/gone-with-the-wind/gender-roles-gone-wind