Ah, parents. You can't live without them but you can't live with them either. One of the great mysterys of life that makes me hate whatever evil god thought that life was a good idea. *shakes fist at the heavens*
I'm sorry I can't offer any serious advice...best thing to do would just move on. I mean, its all over now, isn't it? Or is it taking a very long time to clean your sister's room? :P