First of all, pellets are not at all natural for gliders and probably don't taste very good. Try feeding half a hard boiled egg (NO salt) and some fresh apple and cucumber. Other than that, it really depends on how old she is. Joeys don't care about solid food until around 6-7 weeks, and before that the mom still feeds them.
You need to get your gliders on real food. They need fresh fruits and veggies and protein every night. Look up Original HPW diet, that's what I use for protein.