Shadow of the Dragon series
I realise you may have a backlog of books to add, but please also add the Shadow of the Dragon series by Kate O'Hearn! The two lead characters are sisters - one 12, the other, not sure but younger. According to the 'stupid laws' of the kingdom, Kira, the eldest must be married by thirteen, but all she wants to do is ride Dragons like her dad (which for a girl is against the law).
Our four-year-old loved the two books (which are begging to be made into summer blockbusters, they're so visual and action-packed.) My wife and I just loved reading about girls who were clever and brave without appearing to be super-human, and who defied convention when it seemed the whole world was against them.
It's sad to see that, aside from Studio Ghibli's glorious back catalogue and these handful of amazing books, popular culture still doesn't seem to value or promote stories of clever, independent and realistic girl characters. I'm really glad sites such as yours exist. Thankyou.