[@Red Wizard]
So, I'm going to assume she's in a very basic cell - solid stone or masonry walls, stout hardwood door with iron straps and bolts, a flap to pass things through, possibly a grill or a slot in the door for talking? A straw mattress for sleeping, perhaps a bed frame or just a wooden shelf built much like the door that it rests on? A bucket in the corner for relieving oneself? Perhaps a spy hole?

Or is this one of your fancy cells?