Vick,
You didn't say 'when' you all plan to travel, but I'm guessing it is within the next few months or by early next year.
If this year, I'd suggest doing a 7-night cruise from Athens to Istanbul on one of the smaller ship cruise lines (like Silversea or Seabourn) You could add a day at the front/end to see a bit more, or to just get over jet lag on the front end. Late summer is a great time to do that, and there are still some specials available.
Another suggestion is to look at Tauck Tours. They are good with all ages, but especially good for more senior travelers, and they stay in very, very nice hotels and are very pampering, not to mention deeper enrichment experiences (like after-hours private tours of the Vatican Museum, etc. or a visit to a professor's private villa overlooking the sea to hear her perspective on contemporary Italian life. They get a lot of repeat travelers, so you know they are a class act. We've been on two of their tours and will likely do more. We met several people who have been on 15-20+ of their tours. It's sort of like the Rick Steves' tour version for folks who want a bit more pampering (luggage handling, even nicer hotels, even richer experiences). But, if a group tour is not for you, still looking at their tour itineraries would give you some ideas of where to go and how much time to allocate. Maybe have them send you a full brochure, as it might be easier than having your elderly relative click on line and easier than you having to print off gobs of itineraries. Lots of pretty photos of places to see. Same thing with the Rick Steves' catalog.....lots of good itineraries and ideas.
I like the idea posted about maybe tying the trip to her heritage, if she has European roots. Maybe you could find an old homestead, etc., if she knows from which town/village the ancestors immigrated. Two years ago, I located a distant cousin in Ireland and our trip as magical, seeing the cottage where my grandmother grew up, and just meeting the distant relative. If she has any information about names and villages, it is amazing how one can actually find relatives nowadays.
The idea of viewing the RS travel videos for inspiration is also a good idea.
If you will be traveling next year (or if you all travel so well, she decides to treat you to get another trip), consider a river cruise thru Belgium and Holland during tulip season. That's a lovely and 'easy' trip. We traveled on Tauck, but many brands offer similar journeys.
Ireland is an easy country to visit. If she loves the Royals, maybe England (no language issues).
And, if she really has an adventurous spirit and wants to go 'all out,' take a trip to Antarctica with National Geographic. We had several 80+ people on our journey, some who did the polar plunge, too (swimming in Antarctica). I have a trip report posted on this site, but send me a private message if you'd like more info. It was the all-time BEST trip we've ever taken, and we've traveled a lot. She (and you) would be the envy of all her friends. (Note: But a doctor's statement that one is fit to travel there is required in order to go with National Georgraphic/Lindblad. But, a doctor is on board the ship the whole time, too.)
Love hearing about people who 'live every ounce of life,' and she sure sounds like she is doing that now........and you might as well enjoy it with her and follow her example.
Let us all know what you and yours decide.