My new rat, Eliza, will now have been home for six nights. Today, when I was going to pick her up (the second time I've actually gone to hold her) she bit me--hard enough to draw blood. I realize that this behavior is probably from her being afraid, but I'm not sure how to handle it. Should I leave her alone for a while or go back and try again? Her sister, Sage, is much more shy and timid, never biting. Is this behavior normal?