Both are to blame. Alexandra, despite her insistence that Scout must become more ladylike, has no experience raising a young girl. Her only child, Henry,
... left home as soon as was humanly possible...
Henry's son, Francis, who is pampered by Alexandra when he visits during the holidays, is an evil tattletale who has been taught by his grandmother that men should be servants to their wives. Alexandra's husband, Jimmy, is happiest when he is fishing and when his wife is far, far away; he is no doubt ecstatic when his wife decides to leave Finch's Landing to live in Maycomb. Alexandra badgers Atticus about his children's lack of a female presence, but when she forces her way into the Finch household just before the trial begins, she tries to take control of his home just as she rules at Finch's Landing. Alexandra can't see the good that Calpurnia brings to the house, and she unsuccessfully maneuvers to have her fired. Alexandra settles in quickly, nagging Scout about her overalls; spreading her views about the greatness of Finch heritage and gentle breeding; challenging Miss Stephanie as the queen of Maycomb gossip; and hosting as many social gatherings as possible.
As for the tomboy Scout, she simply prefers the company of boys and men.
I was more at home in my father's world... Ladies seemed to live in faint horror of men... But I liked them. There was something about them, no matter how much the cussed and drank and gambled and chewed, no matter how undelectable they were, there was something about them I instinctively liked... they weren't--
Scout resisted nearly all of Alexandra's attempts to turn her into a lady. Scout does show her aunt a begrudging respect, but there is little that the two can agree upon. Scout can't understand her aunt's "preoccupation with heredity," and Scout disagrees with Aunty's belief that other families fall well beneath the Finches on the Maycomb social ladder.
Aunt Alexandra fitted into the world of Maycomb like a hand into a glove, but never into the world of Jem and me.
As for being forced into more ladylike habits, Scout does give in to her aunt at the end of the Missionary Circle tea, admiring how she can change from one emotional extreme to another in a matter of seconds. But Alexandra's biggest breakthrough comes at the end of the novel when, after the children have been attacked by Bob Ewell, she shows a true caring nature, lovingly referring to Scout as "darling," and,
... in her distraction, Aunty brought me my overalls. "Put these on, darling," she said, handing me the garments she most despised.