I would really advise against getting another rabbit.  Two rabbits can get along just fine until they don't.  Then it can get pretty bloody. In addition to the above suggestions, you might set up a heat lamp. Just make sure the rabbit cannot reach the cord.  How did the rabbit look when you checked on her?  Did she look relaxed or was she all hunched up? Generally rabbits tolerate cold a lot better than they do heat. Do you have access to a nest box? if you can borrow one you could put straw and shavings in it and the rabbit could shelter in it if it was so inclined.  Moving the rabbit from a cold place to a warm one and back is hard on them.