Phantom pain is a great suggestion. Nymeria's behavior could also stem from the left leg area feeling too exposed to her causing her to feel helpless around Tybalt. Sounds like you have gotten a LOT of Great advice. Keep up the good work. It will all work out in the end.
Don't forget to be watchful and understanding of the declawed cat's behavior. Cats don't complain like dogs do, so we need to be sure to watch and listen to their actions. There are several signs that things have gone wrong: Infections/odor, limping, favoring the declawed paws, avoiding the...