Here's a good look.
https://youtu.be/k5X86nD_WS4
That is a great video. Along with ball position at 12 o'clock, lagged lower arm and upper arm rotating in, what else should I look for?
Here's a good look.
https://youtu.be/k5X86nD_WS4
What should a relaxed and natural follow through look like?
The video shaker1 posted is good. College or other high level pitcher's follow-throughs may not be the best when looking for "loose and relaxed" because it can vary depending on the pitch being thrown.
I have not been able to find a simple definition of HE on this site, is there a thread that explains it?
DD started with a new PC today. The coach had her bring up her arm after the release and stop her arm so the her elbow was pointing to the catcher. Is that HE?
In fact, I think if you're forcing yourself to emulate "relaxed and natural" you're probably not accomplishing much of either.
If your DD is just starting out, I would post a couple of videos on here, one from the side (throwing arm) and one from the back. There are numerous posters here that are very knowledgeable in IR who are very willing to help. I've reached out to several here myself. Tons of great info in the stickys. Start her out with IR and don't look back. Some of the very best info out there IMHO.
I like the whip--looks pretty good. Drive can be improved using the 2 Step sequence. Adduction (pulling in together) is probably the biggest thing I'd focus on right now.
To start, I'd back chain to work on pulling in together. Notice how her back leg is staying behind from 12 o'clock into release and how her glove is just going along for the ride? Use them both to pull in together from about 12 o'clock on.
See how Amanda is already adducting both her legs and arms at 12?