She most likely is a nippy stage. All of my gliders have been older, so I don't have first hand experience with joeys and adolesence gliders. My Ollie, who was approximately 4 yrs old when I homed him was very nippy, out of nowhere it seemed. He wasn't biting any blood drawling bites, but still hurt. He's calmed down now and does this less frequently it seems, maybe because he's more settled with me. My girls were around a year old when I homed them, they were my first, Skadoosh would just give a little warning nip if she didn't like something, Lulu was fierce, a fear biter, but she's more like Skadoosh now, rarely biting and only warning nip for the most part.
Another factor for biting is a scent you may be using, such as soap, washes, or lotions.