Elbow 'direction' is a result of handset, grip and turn-the-barrel mechanics. Without seeing it hard to understand exactly what she is doing but her 'problem' isn't where the elbow points but needs those other elements cleaned up. Start with the cause not the effect.
NOTE: Instead of the chair demo, try standing with your back against a wall. Make sure both shoulders are touching the wall, or as close as you can get based on your range of motion. Hold a bat in a typical position. Now pinch/load your scap as you typically would. As your rear elbow goes back, what happens to your front shoulder?
"Once you stop learning, you start dying" -- Albert Einstein.