Low temperatures are not as big of a worry as high. If it’s a huge difference from what she was in previously it may be a problem, since she wasn’t able to adjust to it slowly. (like going through fall to winter adjusting to a colder house temp) Heat above 78 degree’s is too hot.
Some folks use the large dog kennels and they can work. I would say especially for smaller buns.
Since she is a lone bun, I would actually want her placed somewhere that is more busy, unless you have like a finished basement, where you watch tv a lot or such. Rabbits are very social, so if you have a lone bun you are her warren.
Ours is a single bun and she is in are dining area, which has a pretty good view of most of the main living part of the house. She’s potty trained, so she stays out during day and only goes back in when it’s bedtime for us or if no one will be home. She does sleep a lot during the mid part of the day, but even when sleeping she chooses to sleep where we are. My computer is in my bedroom, so she will lay against my wall in here while I’m on it. Sometimes under the parrot cage next to my husband out in the living room, sometimes next to the dog..which is usually by the heater in the winter months.