Lights can have something to do with it, and I would take her to the vet to be on the safe side, but it's possible that it's just her personality OR... Does she have another glider that lives with her? If not, then chances are she's depressed.
About 8 months ago I rescued and rehabilitated a year old boy. He came to me seriously neglected and malnourished. He'd been locked up for six months alone (not being taken out) in a small cage with only a ratty sleeping pouch, a water bottle, and a metal measuring cup that sat on the bottom of his cage for food. His cage and him stunk to high heaven.
For those first five months it was just him and me. It took a lot of work with him to overcome what he'd been through, but we did it. He's now the quirkiest, funniest, all-boy glider you've ever seen in your life. Alternating between a Rambo and little boy mentality.
My point is, that even though he eat incredibly well, was healthy and in a huge cage with plenty of toys and spending hours with me, I noticed he still slept alot, sometimes most of the night. I do believe now that this was a sign of depression because as soon as I rescued my two girls and brought them home, he perked up. And when it came time for them to all be together in the same cage, I could just see the change in him. Now he PLAYS and PLAYS most of the night with his two new friends and they all sleep together in the same pouch during the day. He's so much more animated now then he ever was before.