actually... sorry, went too deep on the solution.
homekit buttons.
you can setup homekit scenes on those buttons. You would need multiple (one for each genre), and one for stop. Adjusting the volume from song to song if needed could be an issue, but when making a scene you setup which music to play (must be Apple Music), and you can set a volume for the scene. a scene can also be configured to stop the music, Or to set the volume to a certain level, while not changing what's playing. Homekit buttons support short, long, and double presses. So if she has the motor control , you may be able to cut down the number of buttons.
Found this one, it's matter over thread, which the HomePod (full or mini) will support. and looks to be fairly easy to press,
https://a.co/d/52bLBnd
There are several options out there, so take a look. Any "matter over thread" or homekit button will work. Thread will be more reliable.
added bonus, you could get a smart plug/s, and add another button to toggle the lights on and off. Easy to setup with shortcuts, so that if the lights are on, a single press turns them off, and if they're off it will turn them on. or do short on, long off.
You can also set timers, so a certain light might go to 20% at night, and off in the morning. or have a certain playlist start playing automatically in the morning. or stop the music at a certain time.
With homekit, you can access all of this remotely as long as you have an apple product (iPhone, iPad, Mac, watch) . Initial setup and adding devices must be done with an iPhone while you're there, Configuring scenes, button actions, and timers can be done remotely, as can activating scenes. When remote you can only see if the HP is playing or paused, You have to be local to see what it's actually playing.
also you could add a motion or presence sensor so you can see if someone is moving around.
Or a door sensor. You can set up alerts on your phone anytime one opens. There's also a log in the home app of when the door was opened or closed (door sensors and alarms are the only thing that log like that)
and with homepods, you can do intercom, allowing you to speak into the house from anywhere. T