Sabin just came in here with a sweet voice asking for a piece of paper. You barked at her, "Why?" She said, "Because." You sighed that sigh that says you're totally exasperated and handed her one piece of typing paper. By the way, we have a whole ream of it. She said, again in the sweet voice, "Why do you have to be so mad?"
Seriously, it was a simple piece of paper.
You can't control every little moment of your surroundings. Especially when you choose to live with this many people. Other people have their own agendas. Sometimes, they're noisy ones. Sometimes they get your brand new dish rags all dirty. But the car has been needing a bath for some time now. Can't you just be glad that someone else was doing something about it?
Chill out, Mom. If she's bugging you with her little friend, put your boots on and stomp out there to spend some time with them. Focus their little energies on the creation of Good instead of the Evil car-washing and bubble-making.