Hi Dudley,
I knew a Sheltie that had been deliberately overbred to be tiny (7 pounds). It was a newish fad in the Southwest to have "Miniature Shelties." Trust me, the owner was an ijiot & was convinced that shelties had been bred from Corgis & Yorkshire Terriers. Yeah, he also wanted a wolf hybrid someday that would "naturally recognize him as pack leader." Few fries short of a Happy Meal, if you know what I mean.
Anyway, this bitch was scared of her own shadow and would hide from everyone, including her own family. After about 3 months of visiting, she would come out to see me...because I had always ignored her when she emerged. Soon, her confidence grew & she would lie next to me & my dogs. But it was funny when her owner came home and tried to greet her...she'd vanish under the sofa again.
So have everyone ignore her for awhile and see what happens. Other than feeding her, just go about your day. She'll probably show up for company soon.
This household was loudly chaotic with a 2 year old toddler & a 5 year old boy. She was over a year old when I met her, so her shyness & timidness had been set long before this. So yours probably wouldn't take so long to see any type of result.
toodles