First place I'd recommend looking, if she has full house access:
In the space under the fridge where the drip tray is. There's a lot of ambient heat there from the compressor and coils.
Plus if you have extra heat pads, instead of putting them out in the open, find all the dark, easily accessible hiding spots you can think of and put heat there. If she's looking for good hiding spots, heat should keep her close to the ones you can retrieve her from.