My best friend is possibly moving to another country for good. How do I handle this?

I have been in your friends shoes. The parents a being selfish, sounds like they already made up their mind. Based on your question I ume you guys are 17? She might be able to stay here and live with you so she can finish school, then she will be an adult and do whatever she wants. If she can even get them to stay til she finishes school then that would be even better, because they might change their mind when they get used to american life again. If I was her I would tell my parents :"ok, but as soon as I turn 18 over there I am taking out a loan and coming back here! my life is in the US!"