After briefly reading the thread, these are questions that might be asked:
How much experience with sugar glider injury or illness does this vet have? Are they absolutely CERTAIN that it is not impacted anal glands? Sometimes the anal glands will begin to swell INTO the cloaca before you see the "torpedo" shaped swelling on the outside of the body.
What other treatment options did the vet discuss with her? Was anything cultured? if so, what?
Yes, I have heard of a prolapsed cloaca before. It is not that common, and is often misdiagnosed. Therefore, it is imperative the the vet be one with a great deal of experience or one who is willing to consult with others.