Drewfus:

I recommend making the $10 investment.  Once your GF has a chance to try this out you will be her hero.  I've only had mine since August and I now never leave home without it.  I carry it in a baggy in a small stuff sack with another baggie with a small supply of toilet paper and a miniature plastic bottle of hand sanitizer.  I've had it with me not only canoe tripping, but also hiking, cross country skiing and most recently out to the fish house.  

I've shared my experience with this tool with other girlfriends who enjoy the outdoors and I have been surprised at the number who already have one or currenly tailor outdoor activities around the size of their bladder.

If your GF has any specific questions...feel free to PM