We can't really call Rey overpowered though. Not until we have a better understanding of her history and the awakening that occurred in her. How much of her ability is due to a past we may not know about? And exactly how aggressively is the Force guiding her in order to accomplish its will?
And on the whole Kylo being strong bit, it isn't so black and white. Kylo is neither a fully trained Jedi nor Dark Jedi but he is inherently strong in the Force, and we know he was hurting bad but managed to channel the pain and anger (punching his wound depicts this) to soldier on and fight. He took a shot from the bowcaster and got sliced a bit by Finn. This gave Rey, who already knows how to defend herself to a certain extent thanks to growing up alone on the harsh world of Jakku, an advantage. And she was still losing that fight until she opened herslef up to the Force.