I wish I could help but I have no words of encouragement or suggestions other than keep trying.
She probably hasn't tried to take a shower because she can't. Have you tried to talk her into letting you help her get cleaned up? If not in the shower how about a sponge bath?
Does she have any elderly friends who are now alone as well? Maybe one would be interested in moving in with her. Cut down on the persons expenses in exchange for helping her daily.
Sorry, can't think of anything else that might help. The only other thing I can think of is if she won't move in with you... move in with her. Sell your house and you and your husband live in hers.