What I am thinking is that since they both are fine together while doing sit that you should just make them work for their food. Hand feeding might be the way to go then move up to putting a few pieces into each dish until Arizona gets the idea that she need to behave during meal time. I know that it is a pain in the butt to have to sit there and put a few pieces of food into each dish but they do not eat that much
I'm also thinking that since there were only 2 puppies left in the litter and she was only 9 1/2 weeks old how soon did this breeder let the other go? Maybe she was under socialized or had to fight for her food as a little baby?