That's a mother for you. Those who fight back end up with problems. Those who everything she says end up with nothing. Best advice is to keep doing what you're doing and staying out of trouble as much as possible, anything that might alert her that you're up to no good is bad. In the instance that you've described it seems that she was wrong, and in that case I'd suggest sitting down with your dad and telling him what happened. If yo really didn't do anything then he'll put in a good word for you.