What's good man. I was in a very similar situation. I started dating my girlfriend for 2 weeks, then she went off to China for study abroad for 4 months. Imagine how rough that was

I kept the passion levels high and things worked out very well
Here's the advantages you already have with her--a strong foundation of a relationship, and it's only for 1 month.
A key point in keeping your girlfriend interested is coming back home and looking FORWARD to seeing you.
Throughout your conversations on the phone/IM/Webcam with her you must give her something to look foward too.
For example "Baby! I can't wait for you to come back and we get to spend Valentine's Day togethor

. I have something really sweet planned for us"
and you must also convey sexuality and create sexual tension over the long distance. I swear by David Shade's Phone Sex Manual to do this.
Remember to never come off clingy or needy. If you're curious about what she did at a club--say it nonchalantly.
"Hey so how was your first clubbing experience in XYZ Country? Tell me some funny stories

"
It's very important to come off warm, secure, and sexual with her.
If she is beginning to feel distant you can bring back emotions by vividly describing and getting her to imagine great past times she shared with you--for example a really cute moment she still remembers. Vividly describe it and start it off like this:
"Hey... remember that cute moment we had at _________" and be very descriptive about the sequence of events that will get her feeling what she felt at that time.
Another CRUCIAL factor needed in maintaining a LDR is communication. You two must clearly communicate expectations, needs, and wants during that 1 month. Set boundaries and rules. Set times for when you two will talk, what is and what is not okay to do (i.e. boys, cheating, seeing other people), and make sure you establish clear communication of emotions with her.
Sorry if this came out all rushed lol--in a bit of a hurry. Best of luck.