It's quite possible she's purebred as the others have said. Dechi mentioned the different body types and this confirms that. I don't remember right now if this came up in a recent thread or just some other info I was looking at but here's a brief excerpt from a different study at UC Davis (and this does not mean there is any disease present).
"One of the emerging problems in Miniature Poodles is intravertebral disc disease (IVDD), something that is common in shorter and longer backed breeds such as the Dachshund and Corgi.
The Miniature Poodle had two different body types: 1) “Correct or square", with legs long enough for their body height equal their length, and 2) short legs and a long back. The latter body type is much more susceptible to IVDD.
Shortening of the legs was first thought to involve a single mutation in what is known as the FGF4 gene. The common mutation leads to what is called chondrodysplasia, a condition that leads to a shortening of the legs and not associated with IVDD.
This mutation has been introduced into many breeds of dogs to decrease the length of long bones and torso and cause some bowing of the front legs. Many Miniature Poodles possess this mutation and its associated phenotype. A second mutation in FGF4 has been recently described (see reference below) that causes a further shortening of the legs and lengthening of the back, but also causes weakness of the cartilage of the spinal discs (Brown et al., 2017). Breeds such as the Dachshund and Corgi have both mutations, explaining the extraordinary shortening of the legs and elongation of the back. The FGF4 mutation has been identified in Miniature Poodles that have suffered IVDD (Brown et al., 2017)."
Link to the study:
Genetic Diversity in Miniature Poodles
If you or whoever gives her her new home would want to do the DNA health testing, it is possible to check for the gene for IVDD vs just short legs/long back.
This company for sure
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If you want to see further studies showing that the location of the gene insertion is the difference between just genetic mutation for shorter legs/longer back vs IVDD
Link to that study:
FGF4 retrogene on CFA12 is responsible for chondrodystrophy and intervertebral disc disease in dogs