Just remember - there are no "quick fixes". Learning to pitch effectively is a constant and ongoing process. Hopefully you guys have a qualified instructor she works with on a regular basis. A shotgun approach to correcting pitching mechanics is guaranteed to drive her nuts and result in a lot of frustrating game performances.
Pitchers are creatures of habit - to a point. Their warm-up routine MUST be exactly the same every time, with no "step skipping". Her mental preparation must be the same EVERY time. It's all about building repeatable habits and her own personal "system" which make her feel mentally and physically comfortable. So, not only are her mechanics important, it's her preparation - both mental and physical - that complete the picture.
Our approach was "less is more". Any time something isn't working, it's back to the basics - BUT she needs to know EXACTLY what those "basics" are. She should come away from each practice session with a sense of "I learned something new today!", not just going through the motions. Eventually (college) she will be on her own, and knowing how to fix things BY HERSELF will be what gets her through.
More on "creatures of habit" - this ONLY applies to warm up and prep, but in GAME situations she MUST be unpredictable! A college pitcher who gets into any kind of pattern is doomed! Practice being unpredictable. Throw a change-up the first pitch every so often. Does your DD have a killer change? College hitters will take the "flat" rise, curve (that didn't curve enough), drop (that didn't drop) deep into the outfield gap. IMO, unpredictable change of speeds is KING.
Sorry for the off the wall thesis, but I see a gal in those videos with a LOT of energy. She puts a LOT into her pitches, and you can't teach that! Get those mechanics polished, and she'll be a fine pitcher.