Control Another Apple Device

I have assisted my 86yo mother with transitioning to an iPhone and an entirely wireless smart home. I am extremely proud of her for embracing technology, however, often there are times when she doesn't understand what she needs to do. Usually, it is something that can be changed in the settings within the app she is using, or she has accidentally gotten somewhere she isn't familiar with. Since she has appointed me as her "personal technical support specialist" I usually help her out. Because I live 21 miles from her, it is not always convenient or possible to drive the hour+ round trip to resolve her problem. Is there a way to remote access her phone? Something like Switch Control but for devices that are not on the same Wi-Fi network? Any help or suggestions are welcomed.