I have had rabbits do it before. Sometimes they pee or poo while doing it. Sometimes there is nothing that comes out. I do not know what it means though.
They can do it when they are excited. You should be careful around intact bucks who are wagging as they may spray.
I tend to see tail wagging when they are excited and sniffing something (usually they are on the pause box and smelling another rabbits pee or poop).
Well she is recently spayed and is being housed next to a male who was just recently neutered. So the behavior seems to be hormones that have not yet subsided