Important Background Information:
I currently own a single female glider named Tickles, I have had her for about three years now. She is a single glider which is not particularly good however she has been fine up until this point. I received Tickles from one of my friends who at the time owned four gliders. One of the four gliders (tickles) could not behave at all with the others and would be constantly fight, so my friend ended up giving me tickles around 3 years ago.

My Problem
Tickles has been good up until this point aside from some over-grooming problem in the past. About two months ago while I was sleeping she started screeching (different from yelping for attention), it is a mixture of crabbing and hissing, I believe most gliders make this sound when they are mad. She screamed throughout the entire night and the next night she continued. I originally thought maybe she was yelling about her nails being too long. However, after I cut her nails the problem continued. Then I thought perhaps she was sick and this was a cough/sneeze chain. So I fully cleaned her cage and even quarantined her for a week in another room (still visited and fed her), yet the problem did not cease. I spoiled her when she first started doing it and she continued so I do not think she is hungry for attention. She makes the sound for hours on end, even when I am not inside the room. My only guess now is maybe something to do with mating.

Here is a link to a video of her making the noise:
drive.google.com/file/d/1EC8JMfWxsqH09M9aR0U23GkUHn9AkqxH/view?usp=sharing

I haven't slept well in months and I worry for my glider's health.
Please help if you can! I will take any information!

Strange. My female made that exact sound every time she was nursing joeys as a way to comfort them, but obviously, that isn't what's going on with yours. I've also heard joeys make a similar sound when they're calling to their parents. She may be lonely and trying to call to other gliders.