We have to split up.cos she is from different country & married.. we still love each other. what to do ?

I am sad for you. Though, I know you are young but take a lesson from this, foresight. Look at the situation before you go into it. Like the metaphor, test the water before you dive in. Miss her, because you will for awhile, though over time you will find a great girl and your friend above will just be a wonderful memory when you are old. The heart feels pain and loneliness at times, it hurts I know. Though without that, you wouldn't know what love truly is.