Next time she visits I would just tell the woman that she misses the dog badly & has thought of getting her own but just feels this certain yorkie is the one for her, maybe crack a joke about cloaning her, try to keep it on the light side. Maybe point out the behavior problems- her not fitting in w/the life style, pooping on the sofa, the bed etc. Maybe the woman will agree that if it was a good home to the right person she would let her go & agree that the friend is a good choice. Kinda try to feel her out, then if she cant take the hint tell her that she wants a yorkie so let her know if she would decide to give her up because she would love to have her. Thats a tough one. I was in this same situation myself with me & a friend who didnt have time & kept trying to breed her yorkie. she had gotten the yorkie from a breeder that gave it away because it never became pregnant... Anyways I just wanted to take her home & spoil her. I felt she should be spayed because there was prob a medical condition causing her not to have puppies. I am pretty cleavor & tried ever route including offering to sit for the dog while she was at work or let it out to avoid accidents. Then I figured I would take it to my house & let her come home to her quiet home with no pee or dodo on the floor, then give her a few days of deal w/your dog
But I never pushed to much & just got my own. I ask what she would take, she didnt know, I may have made a offer & then I just said if you decide to let her go let me know. I wonder if she still has her? It wasnt a horrible situation but I felt my house was more pet friendly & that half the time she wasnt sure if she wanted the dog either. Anyways I hope it works out. I think she should try, you dont know if you dont try.