Getting married at 19?!

My friends sister (I’m very close to her) is getting married to a guy she’s been dating for 5 months. They literally live across the country from each other. Since they’ve been together, they’ve only been around each other for 2 weeks total. But they have known each other for a long time and the guy she’s marrying is a good guy. But I really do not think she should marry him yet. I think that before you marry someone, you need to know them a lot and be around each other a lot or live with each other. UGH I think this is such a bad idea because of course, when they do finally see each other, it’s gonna feel amazing and magical because they never do see each other. What do you guys think?