Since you're a couple now, I'd go with something personal - for her to remember you... maybe even a little cheesey that you can laugh about...
One of those build a bear teddy bears, with a voice implant with your voice saying something nice to her -- dressed up as darth vader or something from star wars.. .
a nice framed picture of you...
OOOH classic maleficent cheese
you're only gone for a week so you don't want to go overboard -but antoher is send a card a day (a real card, purchased in a card store.. can be funny, can be sweet can be whatever..)(starting before you leave so that each day you are gone, she gets something in the mail. every day while you are gone... Put stuff in the card - stickers... pop rocks... anything flat... (I am the card queen.. it's fun actually
