I would say Misty is the luckiest cat of the day today! The pics show that you have been taking excellent care of her and she is just beautiful. How could they not agree to let her be a house kitty? Talk to her and tell her she has to be a good girl in the house and then she can sleep with you and be true diva type kitty.
I'm very happy that YOU get to keep her...her previous people don't deserve her.