DTI??

Can you request a WOCN consult? I have never seen a pressure sore in the area that I'm picturing, but suppose it's possible if she had a big wrinkle under her leg, or maybe if she sits with legs crossed and increased pressure on that "bottom" leg.

I second the WOCN consult.

It sounds to me there is a very high possibility of it being a DTI. DTIs are not your typical pressure injuries and can really occur anywhere. A big factor is shear, and it sounds like that area of her thigh has the possibility of being exposed to a lot of shear if she was not adjusted in her wheelchair correctly and was not pulled up in it correctly if she had started to slide down.

This article is on the older side, but scroll down and look at the section on shear. Here is just a little bit on shear and muscle:

"Muscles and shearing. Muscle is the most sensitive tissue to shear because the longitudinal layering arrangement of the cells and bundles of muscle fibers are packed together by connective tissue (perimisium) with different stiffness properties than those of the fibers.37 Hence, packed bundles of muscle fibers tend to slide upon each other when the tissue is weight-bearing. Even inside the muscle fibers (cells), the molecules are arranged in longitudinal layers that enable them to ride over each other as they contract, ultimately effecting a contraction of the entire muscle. When muscle tissue experiences shearing, the deformity of the cell membranes is disrupted, spilling the contents into the extracellular fluid.38 Hence, a DTI involving muscle destruction actually creates rhabdomyolysis (breaking apart of muscle).39-41 DTI-related rhabdomyolysis, if detected, is limited to pressure/shearing on areas involving skeletal muscle (usually the trunk and muscles on the limbs). If a DTI occurs on an area of the body that does not involve muscle tissue (extremity bony prominences such as ankles, elbows, heels, feet, and scalp, or DTIs limited in depth to the subcutaneous fatty tissue), the serum creatine phosphokinase (CK) would not be elevated, nor would there be myoglobins (muscle protein from dead muscle) in the urine." (Quote button not appearing)

http://www.o-wm.com/article/review-deep-tissue-injury-development-detection-and-prevention-shear-savvy

Overweight or underweight?

Even though someone might be considered 'muy meaty', it can hurt and become sensitive if seated in one position too long.

Check out if there is some kind of seating cushion/pillow/wedge in use. If that's just not in the 'right spot', the meaty posterior thigh gets pinched.

Might need Therapy to really evaluate for a better seating device.