I think you have a great start on it. Hopefully as Mary took to you she will slowly open up to the other cats. It may take you a bit to get her there. You do have a back up plan in case it doesn't. I have a favorite cat behaviorist I love to watch Jackson Galaxy-my cat from hell. But he answers people. Maybe it would be a good idea to check it out and send him this post. Want Mary to be able to enjoy your house like the others. You are such a good cat parent. I say bravo to you @manorvillemike