Hi emmerson
I bet you wished you'd never asked now!
No, there's no such thing as a dwarf SBT. The breed standard is 14-16 inches to the withers for both dogs and bitches, there are weight guidelines within that height but those will vary between the guidelines due to fitness (with muscle weighing more than fat).
I've heard of people claiming they have a dwarft SBT before.
Basically, if the lady has paid money for it, and told it's a drawf SBT, they have been ripped off. From what I have heard of this previously, the dogs can be a mixture of two or more breeds of dogs (mongrels). However, it is possible it has been bred from two tiny SBT's. Any decent breeder should not breed from animals which don't conform to the breed standard.
There is also no such thing as an Irish Staffordshire Bull Terrier and an American Staffordshire Terrier (AMSTAFF) is a pit bull.
There are miniature English Bull Terriers, but again they are taller than your cairn.
I have seen taller SBT's (16-19 inch to the withers) but again, they have not been bred with the breed standard in mind.
Serious owners will normally use the taller non standard Stafford in athletic type events such as coarsing, weight pulling, althetics going over an A frame, scaling an extremely high wall, diving and racing. Some of those events are absolutely amazing to watch and the fitness levels of the dogs makes me extremely jealous. The dogs love it.
It more than likely is a nice little dog but shouldn't really be used for breeding, it should be castrated or speyed.
Do you know how she came about it, did she buy it through an advert, from a breeder etc. I'd really like to know a little more as this has been raised on forums before.
Lisa