Rebuilding Friendship

I had a super good friend. She always talked to me and asked me how I was doing. She and I started conversations just as much as each other. We did video calls all the time. We did everthing together at school. We confided in each other when times were tough. Now she has moved overseas. I was obviously sad and so was she. I never even got to say good bye. Our friendship has started to fall apart. Obviously before she moved she was very busy and didn't have time to talk to me as much as she used to. She missed a lot of school etc. Our friendship sorta started to fall apart. Now, with time change and everything it's difficult to find time to talk. What can I do to rebuild this friendship and get it back to where it was?