I would also take the snake with me. You can crank the heat up in the car so the inside temp is in the low 80's and she'll be fine. Just keep a thermometer in the passenger compartment so you can monitor the temperature and don't put the tub directly in the airflow from the heater.
I would have her in a snake bag, which would be in a tub w/ a VERY secure lid such as a Sterilite latchbox while in the car. At night you can set up a heat pad, t-stat, and the tub while in the hotel. I'm leery enough of escapes that I'd pick up a pair of non-stretchy nylon luggage straps to make sure that lid stays on the tub in the hotel, those are $7 at WalMart.