This is definitely a situation that warrantes immediate veterinary care. If you already have an established vet for your SG, please take her in as soon as possible. I you haven't established a relationship yet, start calling to find a local vet with some experience.
She may be experiencing hypoglycemia (critically low blood sugar), an infection, metabolic bone disease or calcium deficiency leading to weak muscles, or even something as severe as a spinal injury.
In the short term, you can try giving her a lick or a drop of karo syrup - if her blood sugar is low this can help her have some energy, but as soon as she feels better, try to get her some protein and more complex carbs for a longer effect.
Nutritional deficiencies or imbalances can become apparent at this age, so her diet may need a review.
How long have you had her?
What diet had she been on?
Any chance of falls or injury?
How quickly did this come on?
Are her back legs working? Can she move her tail?
Since posting my question, I did take my sugar glider to my local vet. He admitted not knowing much about sugar gliders but thought she was dehydrated and her body temperature was too low. He gave her fluids and an antibiotic shot. When I brought her home I made a baby joey formula and started feeding her every two hours and giving her water. She was able to drink water and eat from a syringe. I put small hand warmers in her sleeping pouch and put another sleeping pouch inside and put her in it. She is now staying warm and is moving around and feeling much better. Maybe the fluids and antibiotic made her feel well enough to eat and drink. I am still watching her and feeding her and hoping she gets better. I still don't know what is wrong with her but maybe the hyperglycemia sounds possible? This started about a week ago, eating less and less until she wouldn't eat at all. She started staying in her pouch and not coming out. I don't think there was an injury and she moves her back legs and tail fine. She is stronger now that she has eaten a little. I have always worried about her diet. She is very picky. She won't eat the staple food at all and won't eat vegetables much. She doesn't even eat much fruit. She mainly eats protien. She eats chicken, eggs and bugs the best. She really loves bugs. Maybe too much protien? I also make a Ledbetters mix that I put in her cage every night and she liked that pretty well but also stopped eating that. I put vitamins and calcium in the Ledbetters mix and thought she was doing pretty well until she quit eating. We have had her for almost five years and we were told she was 7 or 8 months old when we got her. Another thing I worry about is she is alone. No other gliders. I didn't feel we could handle another glider and was told she would be ok with human companionship but she has never let us handle her much. My vet said if she rallies over the weekend to bring her in Monday and another vet will be there that knows a little more about gliders. So I am waiting and doing everything I can to help but I really appreciate your time and help.
I'm glad you took her in. The fluids are very likely a major part of her improved comfort. Dehydration can have huge effects on the body, especially in little animals.
The diet you are describing sounds reasonable - any chance of any change in the ingredients that might have made her sick? Most SGs really like insects, eggs, and other protein sources - it's unlikely that the protein alone would cause a problem, unless she eats that to the exclusion of other foods.
Hyperglycemia isn't likely unless the vet included some sugar in the fluids he gave her.
If she was developing a systemic infection (sepsis), the antibiotic injection could also be a factor in her improvement.
Companionship is very important to SGs, and a lack could be a source for depression or decreased survival drive. Companionship provides warmth, interaction, environmental enhancement (play), and some competition, which sometimes helps improve eating.
Before pursuing any new SGs, try to get to the bottom of her illness with the more knowledgeable vet - hopefully he or she will be able to help diagnose her problem.
Keep her warm, keep providing fluids, easy to eat foods and foods that she likes until her appointment on Monday.
I hope she continues to feel better - good luck!