
someone else will prob reply and give you more advice but you need to take her out on her own as it sounds like she is barking out of frustration because she isn't allowed to play, not being rude but you are probably 'just the escort' and not nearly as much fun out or as important as your other dogs.
If you are out with just her you will be the main source of entertainment and you can get her focused on you and to look to you for games and fun rather than Lucy and it will be easier to stop her 'mugging' Lucy other times.
Chris