Where are you reading your temps from? Ontop of the substrate or at the surface? Bps can and will burrow, so you really should be aiming for 90 deg on the warm side and 80 deg on the cool side at the surface, under the substrate.
I would also get 2 identical hides, that way she doesn't have to choose between comfort and the one that makes her feel more secure.
How are you warming the prey? Are you using your temp gun on it? Striking on the side and then dropping it is sometimes indicative of the prey item not being warm enough. Thaw in warm water until completely soft all the way through, then hit it with the blow dryer on the head for a few mins.