Generally a healthy cham will shed fairly quickly. One of my girls shed her entire body in a day (including her face and eyes). When I see them going into a shed, I up their humidity to help, and i usually bring them into a steam bath in our bathroom to help it along. As far as guessing ages on chams, I can't help you there. Hopefully someone else will be able to chime in! Do you have any pictures??
How old is she?
Young ones shed very fast, once they start, it's only a few hours before they have most of it off.
When they get older, they shed less often, and usually in patches.
Be sure to mist her several times a day to keep the RH high enough to help the shedding process.
Also, if she is 5 or more months old, it's time to think about making a egg laying box.
You can just leave it on the floor of her cage, keep it moist, and she will dig in it when she is ready.