I have fostered several dogs from our local shelter before we did a dog show, but it was short term and they weren't from Puppy Mills!! I do have a rescue pug that we adopted that has a very stand offish personality, but we just let her do her own thing. She is crate trained and we leave the door opened, she finds her way out once in a while for a scratch on the belly and to eat and drink but doesn't require much attention from us.
You sound like you are doing everything right, KUDOES to you and your Mom!! XO
The way to know LIFE is to LOVE many things!- Vincent Van Gogh