Depending on how much time you have before your camping trip you could train.
Start by taking walks around where you live, preferably "cross country" style walks would be best (you know on the grass in open fields up hills stuff) slowly increase the time that you spend walking, first two weeks might be half an hour next week make it an hour and so on.
Also try walking with weights in a backpack or buy a weighted vest, this will get your body use to any gear you may have to carry and of course SLOWLY increase the weight you carry to get used to it. I can't stress this enough, make sure you are mindful of the weight and how you're carrying it it is amazingly easy to hurt yourself using any sort of weighted work out, this one especially since you'll probably be getting your back involved. Makes for a decent work out too if you ever plan on losing weight (I mean that in the nicest way possible).
You could also just ask your "camping partner" how to get ready for it she might consider that something nice to do with you.
