Around 6 months is a good age to change the cage, at that point she'll be of adequate size for an XL Reptibreeze. At around that age my veiled was restless and started clambering to get out of his medium Reptibreeze at every oppertunity, which was a clear indicator that he was ready for an upgrade, so I quickly switced him over and he's been as cool as a cucumber ever since.
Ours just hit 6 months and already upgraded to a 24x24x48 dragonstrand. Its not completely set up yet but it looks awesome. Cant wait to put him in there. Our cham needs to be hand feed due to tongue problems so working with the smaller cage is easier for now.