Question about having camper setup in near freezing temps.

30 degrees for a couple hours isn't enough to damage anything. I'd put water in the tank though, because that large mass of water will take substantially longer to freeze. I would use an electric heater rather than propane... the propane costs will quickly start to add up, but a 1500 watt heater will do fine heating that small of a camper. Heck, you could even put the heater on a timer that comes on an hour before she comes home to save from heating the camper all night.

Tell her to stay safe!