Why don't you just divide out portions for your girlfriend to feed the bettas? You can put each day's food in one of those daily pill containers for her to just dump into the tank. I'd recommend feeding them less than normal, to minimize the risk of water quality issues, but you'd be fine not feeding the bettas either.
Personally, I've heard nothing but bad things about vacation feeders (and I'm not too sure if they would work well in a sorority setting), but if you want to use them, go for it. I would also do a bigger water change before you leave. Otherwise, looks good!
Edit: ^ beat me to it about the pill containers