I have taught, many a person, the basics of how to shoot in fully manual mode in 20 minutes that have never used a DSLR camera before - and they can do it - it doesn't mean they are fast, it doesn't mean they don't have to think, and it doesn't mean they will fully remember it the next day - however, it is all very doable (see picture below of me teaching my 6 year old in 30 minutes last summer how to fully use a 1DXii in manual with bounce flash).
This is what I do
- F2.8, F4, F8 (1 person, 2 persons, everything in focus)
- 1/100, 1/200, 1/1000 (people posing, people moving, sports)
- single point focus, use joystick to put focus point on what you what to be in the most focus
However, given what the original post was about, a person married to another person, who owns two cameras themselves, and sounds like potentially on walks or other, may want to start trying to learn as well while out on these adventures together. Candidate doesn't use cellphone to take pictures etc.
My original IPhone 8 or Samsung Note 8 is a real suggestion - learn to take pictures, find out about filters (easy processing) and post a few to FB to her close friends or family while following her partner around - sounds like a good idea to me.
My second choice is buy a very modern, lighter, less bulky mirrorless camera, that produces excellent jpegs sooc, such as a Fuji X-T2 or other - (Sony 6500?), with their fast standard zoom 18-55 F2.8-F4 (or similar). The advantage here is that this can also make a nice travel camera for both people. Make the experience about producing good jpegs sooc, but it can do raw if desired.
My 3rd choice is the $300 used Rebel and kit lens just to start learning and then resell it in 12 months if this is really something of interest.
For me personally, I have found that having participated in many different activities in my life, that the buy cheaper used to start and or buy the prosumer equivalent immediately, has always worked out better because it is either a fling that will pass (generally never happens for me) or I want to do it and want the proper tool for the trade - i.e in this case, for the candidate mentioned, the $1200-$2000 modern Fuji or equivalent that can be used happily for years to come.
The one issue I have with older / cheaper introductory consumer type cameras is that the control dials are general NOT easy to use - in contrast, put a 5D4 in a beginners hands, and it is just so much easier to teach and use - this is the feedback I have gotten over, and over again, when I teach people - if the dial layout is good, they can and do come up to speed so much easier (and it is enjoyable), with a well laid out camera (easy to find and operate, Shutter (finger) , Aperture (thumb), ISO (thumb and finger) and Focus point selection (thumb) - all while their eye is looking in the optical viewer.

IMAGE LINK: https://flic.kr/p/KWrwbU
learning the 1DX_ii and bounce flash
by
Paul O'Neil
, on Flickr
Hockey and wedding photographer. Favourite camera / lens combos: a 1DX II with a Tamron 45 1.8 VC, an A7Rii with a Canon 24-70F2.8L II, and a 5DSR with a Tamron 85 1.8 VC. Every lens I own I strongly recommend [Canon (35Lii, 100L Macro, 24-70F2.8ii, 70-200F2.8ii, 100-400Lii), Tamron (45 1.8, 85 1.8), Sigma 24-105]. If there are better lenses out there let me know because I haven't found them.