Why not just install Pandora on her tablet? That's what I did for my 80-year-old, technology-challenged mom on her Android phone. I created a Pandora account and added 3 different stock Pandora "stations" based on her musical preference-- a "classical" station, a "doo wop" station, and a "golden oldies" station. All she has to do is launch Pandora and it starts playing music. If she wants to change the channel, it's easy and intuitive (2-clicks away). If your mom doesn't need multiple "stations" or you create one merged station from multiple genres, then it's ridiculously easy. Just launch Pandora and it plays music, displaying the artist name, song name, and album art. It will continue to play in the background while you do other stuff on the tablet.
By the way, I also entered my mom's Pandora account login-credentials into her PCs web browser, her smart TV's Pandora app (at one house), and her smart Blu-Ray player's Pandora app (at the other house). Now she can easily launch Pandora on any device. For her PC, I put a Pandora (web browser) icon on the PC's desktop (and in the task bar) so that she can just launch Pandora with one-click.
