How about renting a Roadtrek or smaller RV and try it out on one of the guided caravans that are offered? They have trips in both the US and Canada, plus Mexico. they have people there who will help and by the end she will be totally comfortable with the "RV" aspect of things.
She might also meet another single person who could be a travel buddy in the future.... it doesn't HAVE to be a man! LOL. She might find a great, outgoing widow or single lady who shares her interest and will be a new, life long friend.
We have met some GREAT people in the Holiday Rambler Club. If she has an idea of what brand she wants to buy, she could attend some Owner's Group camp-outs and get involved. I agree that making contact via a "camping" club or similar venue would be the best place to start.
Many years ago a small Toyota RV pulled into our driveway. It was an elderly friend of my father's who was on his dream US tour. His wife had died and he had found a much younger, single lady (previous neighbor in the apartment complex) who agreed to accompany him and help him out. He had some health issues and needed a younger person along. And his family wouldn't help (they wanted him in a nursing home so they could live in his "nicer" apartment!). So he was literally "spending their inheritance" by paying for not only the trip, but he "hired" her at her regular rate of pay as a nurse's aide at a local hospital. That way she would have something to live on when she was done traveling with him and looking for a new job. She was a very nice young woman who lucked out and got the trip of lifetime with a very pleasant gentleman who treated her like his granddaughter.
Edit: I just remembered that their 1 year tour lasted nearly 4 and included Canada and Mexico... and he died on the road - happy. We rec'd postcards once or twice a year and my Dad sat at the kitchen table and chuckled... he knew the "kids" (and grandkids) and thought they were the biggest bunch of mooches he had ever met :)