She only spawns in level 2 of Caverns of Frost which are not guaranteed to spawn. Chiltara herself is also not guaranteed to spawn, and does not guarantee a drop of the Gibbering Gemstone.
As of patch 2.4.1 it appears that she spawns a large percentage of time, but getting the gemstone to drop has a very low percentage. She usually appears right at the end of the cave, be it by the Resplendent Chest, the Teleporting Stone or in a dead end tunnel.
In combat, she has Orbiter and Frozen affixes.