The Princess Knight by Cornelia Funke
King Wilfred has three sons and he is raising them to be good at all things knightly: jousting, fighting with swords and giving orders. Then the queen has a daughter and since the queen dies shortly after the daughter is born, the king decides to raise his daughter the same way he is raising his sons.
Her brothers make fun of her because the armor and swords are too heavy, but she is determined. She practices in her own way and with a lot of determination and work, ends up being better at all things knightly than even her own brothers.
As the princess’ 16th birthday approaches, the king decides to have a jousting contest and whoever wins will win her hand in marriage. I bet you can guess who wins the jousting contest…