Of that same era (just a year before):

https://www.npr.org/2012/04/13/150566153/airbender-creators-reclaim-their-world-in-korra

As for Korra herself, the show's creators imagined their headstrong heroine as the kind of girl you might meet on a snowboard. "She's muscular, and we like that," Konietzko says. "It's definitely better than being a waif about to pass out. I know, I look like a waif — who am I to judge?"

Some Nickelodeon executives were worried, says Konietzko, about backing an animated action show with a female lead character. Conventional TV wisdom has it that girls will watch shows about boys, but boys won't watch shows about girls.

During test screenings, though, boys said they didn't care that Korra was a girl. They just said she was awesome.

Not to speak of the fight over two girls holding hands in one scene.