I have aussies, and one day I will get a mini
I DO know alot of reputable mini breeder who health test, show their dogs and as with any breed there are alot of unreputable ones
who will breed to anything to get that small size.
15 pounds, is a little light even for a mini, are you sure she didn't get a TOY aussie, and yes unfortunately those are out there
A friend got one at, of all places a flea market
Cute little thing, didn't get over 12 lbs, but looked pomeranianish..
If the puppy is all white, I would have it checked for deafness
My rescue came out of a merle/merle breeding (frowned on), two of his litter mates were lethal whites (deaf), two were fine, two 'iffy', health issues.
The mini's are usually shown in ARBA (Rare breed) and registered with them.
The majority of mini's my friends have , range in weight from 22-30lbs.