I've seen balls that you put a treat in so the ferret can work on getting the treat out again, that might work. Balls with different textures might be good for her. I've never had a deaf ferret, so this is all just brain-storming. You can also put treats in the small Kong toys.
We bought a cat toy for our four ferrets that moves and flashes. We can't leave it with them without supervision though because Nigel can flip it and take the wheels off of it in less than a minute.
I'm sorry about Tachi, ferrets just never live long enough.