The skier's stride needs to be shortened to allow for a complete weight transfer commitment. This will eliminate the slapping noise you can hear resulting from her glide ski slapping behind the set ski. A committed drive of the glide ski will result in carrying more momentum forward. Sorry to be a pain, but I went through the same instructions from the Norwegian national team coach.
You made it sound like there was another technique to be more efficient on these terrains. Is there? I’ve been crosscountry skiing for over 30 years now lol if there’s another way please let me know! She looked like she had a really good pace going, and I’m still working on my technique to this day. Getting faster in my older age haha