Oh, I know she's a good girl. I think they just get bored and find something all of a sudden that didn't occur to them before like the corners of the carpet. You might have one that never chewed anything, but then one day something is chewed up and it seems so out of character. I don't think they really are out of the chewing stage until they are past two. I wish I could remember, but you do forget those things after so many years!
It probably won't be all that much longer before you can leave her with the run of the house.