Being self-sufficient leads to isolation, and isolation doesn't work as we grow older.
Yes, you can manage and handle things and look after yourself but you are very unhappy.
Something isn't working, even though it may have worked in the past. New behaviour for you would include making a conscious effort to reach out to other people.
Rightly or wrongly, her life has not turned out the way she expected, and she feels she lacks the mental and emotional resources to turn it around again. Growing old without the support and company of people close to you is tougher.
So please, those of you over 70 who have got through a crisis like this, write and let me and Sylvia know how you did it.
You could also use the computer to research cultural, educational, social opportunities in your area. I see that your local town has an alternative health centre that offers all kinds of services.