I am a small, older woman with severe arthritis. I found that the 2007 Toyota Camry’s automatic transmission center console shifter is very easy to shift, more so than the column shifter on my previous cars. Likely the shifters in current Toyota vehicles of various models are similar.
I suggest you take your MIL shopping for her to find what vehicles she can comfortably enter and exit, sit in in comfortably, see out of well, can manipulate the shifter and pedals safely, etc. Once she can narrow possible choices to a short list, then start test driving.