D.,
I love that you are so caring and kind. It is difficult to watch someone we care for go through tough stuff but when people are grown all you can do is give them your best advice and keep it moving.
People will either take the advice or not. It is their choice. We have our own journey through life. She must take hers. Her culture is different and she is equipped to handle that or not but she has to take her journey.
As for the school, hire a new teacher. If she is willing to train and prepare that teacher great, if not then you need to put on your management hat and make some decisions. Your schools reputation isn't just about this teacher but also about you as the administrator and your ability to pick people that best represent your companies ideals and practices. You may loose some students because of the change in teacher but you owe it to the parents to be transparent about the transitioning to a new teacher. I doubt you will loose as many as 15 students and if you did I would question how people see you as a administrator and facilitator.
If you are a praying woman, I would strongly recommend prayer as a source of guidance and direction.
Please let me know how this turns out for you.