Torso is slightly forward (to catcher) and slightly out over the power line, and torso is too rotational. Whenever your shoulders get forward, around, or out... the arm follows. Her posture should be such that her arms contact her side in the exact same place they would when standing upright... which is nearly always behind the iliac crest.
Have her stand upright, with her arms at her sides, with "good posture". Note how "deep" the arm is on the side of her body... the part of the arm your looking for is about 3 inches below the elbow... where the arm "doesn't tan" in the summer time. Wherever her arm comes to rest in this position... should be where we would see it in a full pitch... IF she isn't trying to "make it happen" versus "let it happen".
In response to your PM: the sprinters posture is good early... during the drive... the posture that occurs during whip... is a whole different subject altogether... and what we are all commenting on. She is doing that drill just fine... it's a drive drill... we are suggesting that she spend a little time doing some "release mechanics" drills... make sense?
"Missing the whip" happens when we don't "shorten the radius" of the circle. IMO, it's a postural/effort breakdown. When the posture is good (doesn't lean forward, outward, or rotate)... our body will receive our arm naturally. WE DON'T WANT TO CLEAR A LANE, rotate into release, or bend in any forward or outward direction. Poor pitching posture exists BECAUSE of TENSION.
"Missing the whip" is a reference to timing of internal rotation. You can be too early, on time, or too late. The pic makes me believe she is not on time... hence the expression.
Once she understands this stuff, take the ball out of her hand and have her "throw air"... loosely and with a slower tempo (take the drive out at first and just have her throw air with her feet at 45-degrees and with a slight step). You'll see that in a matter of minutes, she'll get it and do it beautifully. HOWEVER... as soon as you put the ball in her hands... and give her a 'forward target'... she'll start exhibiting that forward effort again. This... is where the journey begins... and is just going to take a sound mind with lots of QUALITY reps.
Lastly... one way to relay this to your DD is to show her this picture... and ask her if she walks down the hallway in school with her arm out in-front of her hips like that. (Put both arms inside the iliac crest - google it - with palms out and show her what you mean) If you need a reference of WHERE the arm should be... look at Matt's clip and the young lady he posted.
She's an athletic talent, no doubt... just needs to improve the whip & posture.