Just make it the small iPhone and upgrade it consistently every two years. People like my wife will buy a new one every time one comes out, Apple.
You can even charge more and put a more recent camera in it. My wife never used the extra wide camera but it would be nice, if it only has the single main camera, for it to be only a generation behind so she can get the larger sensor for taking better low light photos. On the Pixel phones you can get a really great low light camera even on the cheaper models.