My advice is to let her join. Cool it off a little, but no need to break up right away. If the roles were reversed, no one would think the girl had to dump her boyfreind or marry him just because he joined the military. If you try the long distance romance and find out it can't work at all, you probably wouldn't make the marriage work either. If it works, you can marry her after she gets her permanent location and move down to where she is. Four years is a really short period. Having a wife who actually is willing to work and do new things could be a great advantage.