We just recently adopted a two year old glider and we're going through the bonding process. She used to have a very poor diet and we're trying to change that, but lately shes been exhibiting strange behavior like biting the bars to her cage. Is this because we aren't feeding her enough? Or is it a sign of boredom or stress? We're trying to get another sugar glider companion for her and we were hoping that would stop the biting of her cage.

I have not seen that in our gliders.
We got one lone glider along with a pair, we got them into a three colony pretty quickly, previous owner had trouble with it.
Our lone glider would go to top of cage and hang upside down, was very jittery. was very skinny, and would do flips off the ceiling of cage.
After we got her in the colony she completely calmed down after about 2 months, started to gain weight, would take treats easy. Only habit she kept was to stay in her own area and take treats, if any of others got near her she go real treat protective.

It sounds like anxiety. A friend would definitely help :)