Any tips on where to travel with an older (and somewhat socially unaware) woman?

Hey y'all! I was just looking to see if anyone had any ideas on where I should take my grandmother abroad. I'm graduating in the Fall and she promised to all of her grandkids that her college graduation gift would be a trip abroad. I did a travelling study abroad semester and would say I'm a pretty confident traveller, but I've been having a bit of trouble figuring out where I should take her for a few reasons:

1. She will be 76 when I graduate

2. She can be a little problematic in the way a lot of older people are, just somewhat out of touch

3. We're both women and we'd be going solo

I'm in pretty good physical shape, probably a bit stronger than the average female traveler, but my Mommom is 4'10 on a good day and has some typical older-lady feet problems. She's also in incredible health, otherwise she wouldn't be offering to take us on her own, but I'd rather not take her somewhere we could be a bit more of a target for pickpockets or anything or somewhere with lots of hills or bad walking infrastructure.

I had originally thought Brazil could be cool, but again, she's a little out of touch and I'm worried she could insult some of the locals, plus Rio is known for being super hilly. I think anywhere south of the equator could be awesome (especially since it'd be winter when we'd go) but she doesn't want to spend more than a thousand on flights so we'd be pretty confined to South America.

Any ideas? I could do Europe again, but I wouldn't want to do Spain, Italy, or Ireland since I already explored them pretty thoroughly. We'd probably be going in January, maybe February, and we'd be flying out of Philadelphia.