Margunn Haugenes' corner reached Rachel Unitt at the far post. But her shot at close-range sped across the front of goal.
Charlton's defenders thought the ball was going out, but Haugenes got it back and crossed for Kristy Moore to volley in at the far post.
Karen Hills and Fara Williams were the unlucky own-scorers. Hills had tried to clear a long pass but she kicked the ball into the net instead.
Williams' shot on the 61st minute went in after she headed a corner into her own net with her first touch of the ball.