I wouldn't worry too much about it. Long-distance relationships rarely work out, and very few people end up marrying their first crush. And it's a looooong way between 13 and marrying age. But with that said, you have to have a first crush, right?
Everything about this relationship seems healthy so far, and with a boy 150 miles away, it's not like you have to start land-mining the yard below her bedroom window or anything.
So basically, I see no reason to either encourage or discourage this relationship at this point. My advice is to just relax, let it be, and live in the moment.
