Even from good conditions if it took a month or more for her to figure that out... I wouldn't have.
Chins are pretty hardy despite what people want to think, they handle moves just fine.
I actually had something similar happen. We got a cat from a lady who had too many cats ( she had four cats in a trailer with two small kids ), she posted wanting to give away two on a pin up board at a store. We took one. Two or three weeks later she called, then her mom called and they harassed me wanting this cat back. Supposedly one of the cats they kept got out and was killed by the neighbors pit bull... literally torn to shreds, and they wanted this one back.
It wasn't my fault they couldn't keep the cat inside, or that this happened, or that they decided to get rid of two of the cats. And I was worried that the same thing would happen to him, so I just told her my daughter was very attached to the cat and I was sorry for her loss. A year later we spent hundreds due to chronic urinary blockages, and he was never right after that. We couldn't keep him in the house because he peed everywhere... we rehomed him to a family with a farm that could keep him in the barn.
I also had a lady who wanted to buy a weimaraner pup from me when I breed them, they only wanted to spend $75 because their last one got hit by a car because they live right next to the highway.... it was a okay, sorry mine are $350 as stated in the ad, good bye.