Rabbits can handle pretty low temperatures. One time the heater broke in my apartment in the middle of winter, and it got down to 55 degrees, and my bun was fine. She didn’t even want to sit anywhere near the temporary electric heater they gave me for my bedroom. Ears aren’t the best way to tell if a rabbit is too cold. They radiate excess heat through their ears, so cool ears just mean that the bun doesn’t have any excess heat to lose, not necessarily that they are too cold. Generally speaking, ears are a poor way to tell if a bun is too hot or too cold. I would be more worried about drafts than cold temperature, and if your bun has a way to keep away from drafts, she’s probably ok. Does she chew a lot? If she doesn’t have a tendency to chew on things like fleece, you can always toss a folded blanket or towel in a box into her area to snuggle with. If she’s a bun who likes to chew on blankets (like mine) then the box is probably fine without blankets or towels. I added a tightly woven rug to my bun’s box. Rabbits don’t often experience hypothermia due to cold temperatures unless they’re left outside. As long as she’s flopping out and has energy, she is fine. She wouldn’t flop out if she was trying to conserve heat. If you notice her doing the bunny loaf with her fur fluffed up more (to conserve heat), you could always try putting a cordless heating pad on the lowest setting in a towel in her area (under your supervision), and see if she’s even interested in warming up. Mine never are. They love the colder temperatures.

70 is very comfy for a bunny. Even 60 or 50. I used to keep my bunnies outside in virginia. They are so much more comfy inside. I brung the thermostat down to 64 at night. My bunniesdidnt use the heat lamp i orovided them outside when the temps were in the teens. As long as they r not in a draught. Rain on a roof could make a bunny nervous. As long as they act comfy, flooped etc, they r fine. Older bunnies tend to benefit from extra heat. Im visiting in texas and the house here is cold, and i have my elderly bun with, and i have him covered with a blanket. He likes it.