Please don't take this wrong, but your story saddened me a lot with a quick question in my mind "Does she know all about this?". You probably feel angry, disappointed and yes, even frustrated, but please don't let her know all about this right now. People might say "oh come on, share everything with your girlfriend, whatever joys and sorrows…" I agree in some ways, but I can see she would feel real hurt. First she wouldn't accept the disapproval from your grandparents just because of her nationality. Then she feels hurt so much by the fact there's nothing she can do about it.
In my opinion, there's no way to deal with this kind of problem except you step back and wait for a moment. It will take time or ages for your grandparents and parents to understand you really care for her, because they might think that you are too young to have a serious relationship, that your love will just fade away in few months, years. Be strong, brave, and discreet. Be yourself. Most important thing is.. to protect her from the hatred and to think what's the best for her. Good luck.