will she one day walk away to die in the woods and I won't be able to find her.
My biggest fear would be the above. Since she is 17 and getting on in years, I would try to keep her inside. But that is only my opinion.

You've gotta do what is best for Mimi. When the time comes, I hope you will be able to do what is right for Mimi. In the meantime, love her with everything you've got, and make the most of the time you have with her.

(((((HUGS))))

Donna