Well, as previously suggested, this is best to be discussed over with her and make the plans together! If you have made the decision on your own, or worse, base on your parents' wishes, then most likely she will leave. If you care about her this much, should let her know the situation you are in.
I was in similar situation apply for carib or DO school. My gf, now my fiancee, is also pretty clingy too and often gets depressed by herself. I made it perfectly clear the least I will compromise is never to go oversea or to carib but med is my dream. If you are willing to make some sacrifice she should understand too.
Don't just call her, webcam her, make visiting her your priority during schools when you have holiday if not busy with school work. If the school is really only 6 hrs drive away, she can go visit you for the first 2 yrs until rotations come right? If you truly cares about this relationship and don't want to
lose her (not the same as worrying she'll leave, that just mean you're determine to do whatever you want disregarding her situation), then you would try to work this out and find the best way that's best for both of you.
Long distance is not impossible, but nobody can only gives without some in return. I will be 6 hrs plane ride away from my fiancee that's working on her own PhD degrees, while we understand that this sacrifice of being apart means we will have to work harder on our education. We also understand our priority to communicate with each other. It's not an easy route...GL