Stasis is a leading cause of death in bunnies, but is also completely treatable if the bun parent is aware of the symptoms. So you must familiarize yourself with them. If caught and treated early, it's not a huge deal, but you literally have only hours to recognize the symptoms and deal with it.
Best article:
http://www.bio.miami.edu/hare/ileus.html
So again, is Nibbles pooping? I'm thrilled to hear she is eating and taking in some fluids, but is she processing them as well? Is she pooping? If you don't know, dump out her litterbox now, refill it and monitor it carefully for poop. None- big problem. Poops smaller than normal - problem. Poops connected by a hair-like substance (often called a string of pearls) - problem.
If poop is normal, you are okay to wait until morning, especially now that she is taking in foods/fluids. If not, she may have a blockage, and that is an emergency.
If you have input and output, though, please don't worry too much. A spay
is major surgery and she is going to react. Us human females normally take up to six weeks off work for the same thing. Of course she is going to feel bad the next day. And week.
I don't want you to ignore major symptoms, but don't worry unnecessarily either. Yeah, I know that comment is not helpful. But she just came through a major ordeal, it will be a few weeks before she gets back to normal.
Just let us know the scoop on her poop, and we can advise you further...