You are correct Nigel in that the Panorama trains run between Montreux and Luzern and involve changes in Zweismen and Interlaken, but the official Golden Pass route actually runs all the way from Geneva to Zurich (or vice versa). Regular Swiss trains run between Geneva and Montreux and between Luzern and Zurich, with Panorama trains between Luzern and Montreux as well as some classic old time rail cars between Montreux and Zweismmen. See the official site for complete details and schedule - www.goldenpass.ch.
While the most scenic portions are between Montreux and Interlaken and Interlaken and Luzern, it's still a fairly scenic ride between Zurich and Luzern. Given Pumpkins locations, it's the only scenic line that makes sense. I assume she is flying out of Zurich, but don't know that for sure, as she didn't say. Depending on how much time Pumpkin has in Luzern and where she is going afterwards, she could take the Panoramic portion to either Interlaken as a day trip, or do the entire route if she is flying out of Geneva. If she is flying out of Zurich, then it's still a nice ride. The other Swiss scenic rail journeys, such as the Glacier Express, William Tell Express and Bernina Express most likley won't make sense.