With Barnhill, I see her getting strong front side resistance, bicep brush interference, IR (albeit not Ueno level of rotation), and as Corlay mentioned very good overlap and lag into release. She also generates excellent spin with her lower arm and fingers as she demonstrated a few weeks ago on an ESPN segment during the Florida game. Lastly she is extremely accurate, throwing her riseball on three different planes, at will.
"strong front side resistance" - I dont think so. Look at her in Knight's still frames. Hinged at the waist at release. That's leaking energy in my book.
"bicep brush inferference" - um... that's not a thing. She leaps and turns open. If anything, she clears her hips and gets zero brush interference. (in the Rick Pauly definition)
"extremely accurate" - that's an impressive thing with her. With those mechanics, its pretty incredible how accurate she really is.
last thing to add: everyone can just drop the witch hunt that she plants outside the pitching lane. Yes, Knight's gif shows her doing it, but it is an anomoly based upon what I am seeing watching her pitch a full game. Barnhill is no Carlson in this regard.