My mother still gets those disposable film cameras and then has the film developed. I feel your pain.
I gusss the biggest question is is that even something your mom wants. If yes, I personally feel like the iPhone is the most user friendly smartphone for older people, but I understand the way people feel about them.
Either way if she wants to learn how to use is, then set some time aside, and go through everything step by step, together, in person. Then either she can take notes, or you can give her a “how to manual” that’s specifically for what she wants to use most frequently.
Something like to take a pic select this icon.
If you can’t find an app, go to Home Screen and click search above the bottom bar. Type the name.
How to get to Home Screen. Swipe up from bottom of screen.
And so on.
That way she can have analog version of what she really needs to know and anything else you can help when you can. It’s not foolproof, but I’ve seen it work well for a lot of things.