My impression from your post is that the dominant personality is narcissistic.
Devaluing others, posturing pseudo manners (learned behavior), BOASTING about HERSELF, are big giveaways.

She may or may not be borderline...you need time to see if that fits.

I have a really good link to explaining how narcissists behave that is more geared to the layman than technical...I had a huge need for this information several years ago--a painful person in my life..and it never ceases to amaze me how accurate this author really is:

http://www.halcyon.com/jmashmun/npd/

I think her husband knew how to handle her. And it is not an accident that they RV'd thru life...no entanglements there.

There is a personality book by Dr. Oldham, which has chapters on all the main types of people, and how to deal with them. His chapter on how to deal with narcissists and maintain your own boundaries is very good.

This is a brief outline of his book, which you can find on Amazon for a song.
It is the best layman's book on personality out there IMO. I have gone back to it over and over and recommended it to others who have loved it and used it well.
http://www.geocities.com/lifexplore/oldham.htm

I know you want to do the best, most compassionate thing. But realize this lady is not capable of empathy, and is really as you observed "like a bull in a china shop".

The one thing for sure, is if you accidentally deliver a narcissistic injury (and you don't know where her "buttons" all are) she will most likely react with RAGE. They all do that. (it may be a little thing to you, but it could be huge to her).

You can email me if you want to discuss this further.

Also, since she is aging... there may be cognitive challenges involved as well. If she is mildly demented, that would
complicate things enormously and prevent her from behaving more rationally. (my husband's aunt comes to mind here-- that
was a huge issue for our family)