You do not describe in much detail what you did. Based on the information
you gave, it does NOT appear you introduced them properly.
They should be introduced in a neutral/ scent free area. bedroom or we use the bathtub. The move to a SCENT FREE/CLEANED CAGE is NOT done till after a successful bathtub introduction. (but again your description is limited)
If the cage is not scent free, the young one is intruding into the older females territory, and could be afraid of territory aggression.
We let the gliders roam the tub, get out sniffing, touching, climbing, a few spats. We wait till they all climb into the ONE SCENT FREE pouch we provide. Once we have a calm and happy pouch with gliders inside, then we consider a move to the clean cage. BUT this is after weeks of sleeping pouch swapping, and cages 6 inches apart.
www.sugarglider.com/gliderpedia/index.asp?IntroducingNewGliders