Sounds like neglect and improper diet.
My glider also had monstrous nails when I first got her, zero glider safe toys. A t-shirt instead of a sleeping pouch... And pellets.
And on top of that she was a single glider. Her brother had apparently died very young.
She was skin and bones and a very unhappy, scared glider.
She seems like she also drags a little compared to all my other gliders.
Here's a picture of her nails back when I first got her.
Happy to say she is doing infinitely better, I've been with her for 6 months and her nails have improved, she put on some weight, she went from a very defensive, scared girl to a happy beautiful girl. Her and I are the closest out of all my gliders which goes to show that adult gliders can bond and neglected gliders can learn to love and trust again.
So if I were you I would do the following:
1. Get a vet to give her a check-up
www.sugargliderhelp.com/links/pages/Sugar_Glider_Vet_Database/North_America/United_States/index.html
2. Trim those nails! Go online to check the safe part to trim, but from my experience it's hard to tell where that is with monster talons. Be super patient and try not to knick her. Reward her and speak to her when you do it so she understands nail trimming isn't a punishment. I use cuticle trimmers. The nails should look very close to normal in a few months.
3. Get her on an approved diet if you haven't already.
www.sugarglider.com/gliderpedia/index.asp?Diet
HPW and BML are the two most popular. BML is high in calcium too and a little more convenient since you aren't required to order anything by mail. I think BML is great for anyone starting out and helps gliders who were improperly fed fatten up and regain health. Mine were on BML for several months before I switched them to HPW. Each diet has certain required fruit and veggie intakes so keep in mind you will be spending a lot more time preparing fresh food than you would other pets. (Heck my gliders eat healthier than I do)
4. Please find your glider a buddy! It will help lift her spirits and be more active.
Keep us updated!