It is all very odd. The fact that she was dehydrated but they found nothing else? Is this a vet that you have used for some time and that you know to be very experienced with gliders? Not all are, but will say they are familiar with them.
It sounds like she is still going to need some TLC to make it through this.
Why do you think she became dehydrated? ie: heater on in house, no sufficient access to water bottle, not enough hydration from juicy fruits/veggies and a nectar like stable diet?
Has she been eating well recently, and what is their diet? Can you think back and come up with anything else that could have been a sign that things were starting to go wrong, however slight. They hide their illnesses for a very long time...up until it is almost if not too late. Diarrhea? Weakness, lethargy, shaking? Change in sleep patterns. Hissing while urinating? Constipation...hissing while trying to poop?
There just has to be more to the story. It's only in her best interest to try to see this through 100%.
So glad she made it through the night and to the vet.