Hands pull back during the stride forward...but her hands are coming back due to counter-rotation of the shoulders, not because she's pulling back into the scap. Scap retraction is an important piece of the puzzle. We see the shoulders turning, but not the hips. For me, I like to see both turn back about the same during the stride (look up "forward by coil"). We also need to be aware that young hitters tend to turn back excessively when working on a tee because they can still see the ball just fine. Against a pitcher, they can't get away with turning that far. Try to replicate what they will be doing on the field. I usually ask them too look up as if they are looking at a pitcher.
Once her heel drops, everything starts to push forward - hands, hip, torso. A big piece of the puzzle is learning to pull with the muscles of the back. Look at video of elite hitters and pay attention to how they are using their back. I also recommend you look into learning about the hand pivot point and how to turn the barrel around a tight HPP to launch the barrel out from the rear shoulder. What we don't want is an arm swing around the spine, which is what we are seeing here.
You talked about her elbows, and "stationary triangle", but she's missing the turn. For her, the base of the triangle stays facing the the floor. This sets up her downward chop through contact. What we want to see is the base of the triangle turning up (towards the pitcher), with the hands being the pivot point for the triangle turn (HPP). The front elbow working up allows the barrel to work in a better path.
I've been posting these a lot recently, and I think they can both help with your DD...
Hand pivot point and barrel turn
Diagonal swing plane (notice how the front elbow works up, and how that relates to the swing plane)
Once her heel drops, everything starts to push forward - hands, hip, torso. A big piece of the puzzle is learning to pull with the muscles of the back. Look at video of elite hitters and pay attention to how they are using their back. I also recommend you look into learning about the hand pivot point and how to turn the barrel around a tight HPP to launch the barrel out from the rear shoulder. What we don't want is an arm swing around the spine, which is what we are seeing here.
You talked about her elbows, and "stationary triangle", but she's missing the turn. For her, the base of the triangle stays facing the the floor. This sets up her downward chop through contact. What we want to see is the base of the triangle turning up (towards the pitcher), with the hands being the pivot point for the triangle turn (HPP). The front elbow working up allows the barrel to work in a better path.
I've been posting these a lot recently, and I think they can both help with your DD...
Hand pivot point and barrel turn
Diagonal swing plane (notice how the front elbow works up, and how that relates to the swing plane)