You could go that route if she doesn't mind two remotes.
I suggested the Harmony because you can program the "function" buttons to display clearly on the remote "WATCH TV" and "WATCH A DVD". You can even change the text to say "Push me for TV" or whatever. The rest of the buttons (off, channel up/down, pause/ff/rew/play,) are like most other remotes, with the same type of labels. If something screws up, there is a "help" button that will generally fix the issue.
Harmony remotes pretty much work the same, so you could show her the different ones and have her pick one that she likes. Most electronics stores carry them.
Either remote method would probably be preferable to her than to have to get up and flip a switch.
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