Were there any girl knights?
As a rule, no. As an exception, yes. Tales have been told all over the world and through the ages of women disguising themselves as men to save cities and kingdoms.
In China, there was Mulan, who took her father's place in the army, because he was too old to fight. She fought for twelve years and was highly respected, but she refused any reward and retired to her hometown instead.
In Catalonia (Spain) in 1149, a group of women dressed in man's clothes fought off the enemy from their town. These women earned the title of knight and had special privileges thereafter.
Joan of Arc put on armour to save France in the 1400s, but she was never officially made a knight.