What is the ruling concerning prayers performed by a girl, where her wrist touched the ground, due to her ignorance of the ruling?

Your past prayers are valid, praise be to Allah. The most you did was commit a reprehensible act (makrooh) among the reprehensible acts of prayer, which does not invalidate it, especially since you were unaware of its ruling. Indeed, the Prophet, peace and blessings be upon him, forbade this, saying: "Be moderate in prostration, and let none of you spread his forearms out like a dog." The meaning of this is not to lay one's forearms flat on the ground like a mat.