She should marry someone who has at least completed the educational requirements for a high school diploma
From what you've said his plan is to finish school and go into the military. What's wrong with that plan?
AND one who hasn't cursed out her family or been jealous of the fact that she 'ignored' him for 5 minutes while she was talking to friends she hadn't seen in months.
That's what marriage is about, I've been there and so will you. I know you aren't happy with your friends decision and you feel she's making a mistake, but she's an adult now. I know you have her best interests at heart, but this is a decision no one else can make for her.