I see how everybody is either pouncing on her or telling you to do stuff that is repetitive and/or time-consuming. I'm here to tell you about the single best weapon people in LDRs have:
the letter.
It's possible that she is just ungrateful and demanding, but you should probably give her the benefit of the doubt first--maybe she doesn't even know herself what specifically would make her feel better about the situation, other than making it what it used to be. But you already know that that's not possible, right? You have to come up with a solution that works for both of you. If she has enough other things going on in her life (support systems like a school, a family, a group of friends, hobbies... these are all great networks) then she is really just asking you to make her feel close to you again. It seems like a tall order, but the letter is weapon number one in combating the feeling of separateness.
I read this great book about LDRs, which cited just about every study ever done on them that was worth two beans. A lot of it seemed like common sense to me. For instance, an LDR's chances of survival depend on factors that have nothing to do with distance - they are the same factors that make geographically close relationships successful, like trust, communication and constructive disagreements (to learn about each other). Then I read the one thing that I never would have thought about on my own:
the letter.
Apparently, the letter has kept hundreds of LD couples together for as long as there was a postal service. This much seems obvious. War, separation, getting a letter to know that he is thinking about you and to know that he is alive - great! BUT, the shocker was that written letters have the same effect on LDRs even today, when we have all of this technology that allows us to communicate without the paper and without the delay.
I have tried this myself. You can talk to that girlfriend of yours six hours a day on the phone and I bet that at some point, she would still be complaining of the same lack of closeness to you. Six hours! You probably didn't even spend that kind of time together when you had a car. And still, she feels this nagging feeling of distance between you two. But letters allow you to focus on the good things, unlike phone conversations. How many phone calls have been derailed by using the wrong tone, or mentioning the wrong thing at the wrong time? A lot of them end in fights.
We automatically tend to view letters in a more favorable light. For one, it shows that you expended the effort and were thinking about her. More importantly, it gives her something to re-read whenever she needs or wants to. It gives her a stand-in you - your words. If she starts to really miss you but she knows that you are unreachable or too busy to interrupt, she can go read her letter and feel loved all over again - and no actual interaction with you is necessary. The best part about this is that a letter isn't expensive. You need paper, envelopes, a pen and some stamps. That's it! I guarantee you that one letter goes a long way. If you could even send her one letter a week, I bet that she would find more comfort in that than spending a whole lot more time on the phone or trying to be together while you need to be doing other things.
That said, if she doesn't like letters, she's inhuman and you should drop her.