After my first roll of Kodachrome I used almost nothing else for 50 years. If a subject didn't look like it was 2X3 I didn't take the picture. Now that I'm into digital I do some cropping (and sometimes try other forms of editing).
I think #625 is a zinc/air battery. They are smaller than some mercury cells and you may need to put a rubber O-ring around the outside to keep it in place. I forget the O-ring number but in most store the bins get so scrambled that you should bring the battery to get a proper fit. I think the O-ring thickness is .073. (The memory is only partly gone.)
While playing with a new (to me via Ebay) I saw the lens extend and realized that the air volume inside the camera must have increased by a cubic inch or two and wondered how the air gets in there. Is there a piston or bellows that repositions to keep the internal volume constant , does the air come in through an internal, filtered, opening or does it come in through whatever cracks and crevices exist? On film cameras a new clean photosensitive surface appears every time you advance the film but with a digital the same surface stays for the life of the camera. I guess I'll have to remember to only turn on the camera in a dust free environment and clean the lens barrel before turning it off. Paranoia makes life more interesting.
I was walking around the docks in Reykjavik the same day American and Icelandic fisherman were brawling in Boston about unloading fish from a factory fish processing ship. Luckily news traveled slowly then.
My experience started taking black and white photos with a 620 (2 1/4 X 3 1/4) black and white photos and developing and printing at home in a closet converted to a darkroom. I pasted the results in albums. Then I moved away from home and about the same tome bought a 35mm camera and soon started using Kodachrome. I bought a projector and screen but realized that I preferred a hand held slide viewer in daylight. When Kodachrome was taken off the market I switched to digital cameras and looked at the pictures on my computer monitor. Then I got a cell phone which allows me to send photos directly to friends or look at them on the phone. I seldom look at any of my older photos and when I do I don't study the details. They serve only as memory prompts. I hope this helps.
a Univex (not the Mercury model). It cost 19 cents at the local Recall pharmacy. It had a flip up wire frame viewfinder and used size 00 Gavaert film, maybe unsprocketed 35mm. Soon replaced for a Kodak Bullet.
There was a company, Stereo-Realist, if I remember correctly, that made cameras, projectors, and slide viewers. They had two lenses at about the width apart of human eyes. They show up on Ebay once in a while.
I too was looking for a possible replacement for a Retina IIa (like the OP) and considered the Rollei but was concerned about the need to open the shutter to collapse the lens. Maybe that issue was solved later. I eventually went to an Oly Pen S and then to a Pen D.
Apple sells small iPhone printers. I haven't investigated enough to know which is best. Back n the day I used to print on double weight glossy, dried in a blotter roll without ferrotyping. Don't know if any similar print media is available in a small wireless printer.
I would skip the zoom and just get a fixed lens camera. As she gets used to that she will start to recognize that would make a good picture even when she does not have her camera with her. And I think going to a class, if possible, where she will hear other peoples questions and thoughts would be beneficial.
Some ocean beaches have parking lots quite close by. Also some farms offer wagon/hat rides during daylight hours. And some scenic railroads are really quite scenic. Good luck.
I would suggest a Nikon L35AF because of its slightly wide angle lens and its use of AA batteries which can be found anywhere. It is an auto exposure camera with manual focus. I can also suggest the Konica C35EF3 for the same reasons. Both have plastic bodies but I have never dropped a camera. Happy hunting.