A great way to understand how to get mentally fit is to look at physical fitness. For most unfit people, exercising muscles that they don't use is unpleasant. What they need is simple exercises that are short, easy to understand, repeatable, cover a range of muscles, and have variations that provide increasing difficulty for advancement. You don't want to start someone off doing power lifts.
If you've been to any gym classes, you'll realize that there's no such thing as an objective scale for exercise difficulty. Squats may be trivial to someone but impossible for someone else. Finding a person's level of fitness and figuring out a good set of exercises that are appropriate for their progression is the key to a good long term fitness plan that actually works.
How about starting her off with something simple like sudoku? I know some may balk at the idea of sudoku being a mental challenge, but it's the mental exercise equivalent of yoga. The reality is that some people who haven't used their brain in a long time may be at a very, very low level. Not a knock on them, just not everyone has the opportunity to use their mental faculties 8hrs a day at their day job.
While I agree with most of your comment, this caught my eye, because that's exactly what "Starting Strength" by Mark Rippetoe (an HN recommendation, I might add) does. Granted, Rippetoe points out, multiple times, to start with the empty bar. It's also probably not a bad idea to have your form checked, although I lifted for a year before doing so, and the only time I've injured myself was a bodyweight exercise (situps, which aren't part of "Starting Strength").
I wrote an app to let you play, starting with playing with one colour, before moving on to invisible.
https://simonduff.net/invisilink to play in your browser, and a link to the Android app. Appreciate any feedback :)
The usual play is to get people from the audience say random words while you assign those words to something you do everyday (the most common tool is the way to work/school) in order.
With training (as you are doing), you can remember long lists of seemingly unrelated things (and the order they are in).
As I said, a bit offtopic, but I found it funny for that old trick to come up here :)
Tried googling it to no luck. Any idea?
1. First floor space is the most expensive (a testable assumption), and only luxury brands like LV can afford it.
2. Brand name on the first floor attracts people walking by into the mall.
Some of the smartest people I know don't actively seek out to improve their thinking skills. Its simply a by-product of thinking more about anything and everything. When it comes to thinking, depth first is the way to go. Start asking questions about everything you see (why is Louis Vuitton always on the first floor in a shopping mall? If I spilled my drink, how long does it take before it gets cleaned up?)
Perhaps the best way to improve abstract thinking skills is to increase your mental endurance and start thinking about things more. Eventually, you are going to start connecting things and the abstraction will start to happen.
Also, perhaps increasing your creativity might also help. Every morning I shuffle a deck of cards and I memorize the order (timed. I started this year at 15 mins, now it takes about 1min 30s). To memorize a deck of cards, you must create a story out of your ass and it helps with your creativity.