Aaaah yes, the military.. I use to be in the Marine Corps, so I can at least give you my opinion..
I'm going to have to agree with xxazurexx.
I have RARELY ever seen LDR work, ESPECIALLY in the military - my own included.
In my opinion she isn't showing you her feelings because she can't. Its superficial. She could be a military groupie. Or just leading you on. Or is a military groupie that is leading you on (90% of groupies are like that).
In any way, I would move on. I know, it sucks. But you will eventually meet someone who actually loves you as much as you love them. This girl is keeping her options open, hence the non-commital attitude, and I can guarantee that there is a line of guys following her home trying to get with her the moment she got off the plane (or car).
I wouldn't tell her that you love her anymore. Talk to her, yes. But don't share any more feelings, and start looking towards the future. You cannot violate her sovereignty, so any more effort in this area would be moot. I would remain friends, and if she comes back to you then its meant to be. But it just sounds to me like shes "keeping your d**k in a jar"
You're never too old to learn something stupid.