I quite agree with what's been said. Brody and Mia are both very personable, well adjusted, well socialized, and love love love people and attention. However, Mia is a bit more easy going at times with strangers, especially children, shying back with some of them...the louder, shriekier, rowdier ones. Brody has a 'line' he's established for himself as "King" of his "universe" and 'some' dare not cross. So far, he's been wagging the whole time and his body language is not one of aggression...warning, rather, that 'there are rules'...Brody's rules...which must be obeyed. He has been absolutely great with some children who come running up and just reach out to pet...other children he seems to distrust and perhaps 'dislike' from a distance...he's shown the same behavior with some adults, too...with no observable provocation on their part. Perhaps it just something he alone 'senses' from their presence...dunno.
Just because the 'doggie' is little and cute is no reason to assume or treat the dog as if you are 'old friends' with the pup...you could come away with quite a bruise or puncture.
I think there is a good chance that they just got off on the wrong foot due to all the upset in the Yorkie's life. However it goes...adjustment or second re-home, I hope the Yorkie's life reaches a new normal quickly. That poor baby's life is completely upside down at present...I cannot even imagine how awful it'd be for them if Brody and Mia were uprooted now.
My heart also goes out to the lady who had to give up her 3-year-old Yorkie. That alone had to be a horrible experience, but on top of everything else she's going through, seems like only the tip of a nasty iceberg.