Yes, two very different events in style and feel. At a very basic level, it's like choosing between going to Christmas Eve church service or a friend's fun sweater Christmas party. Both very enjoyable, but evokes different emotions and depends on your personality and what will be the most fulfilling event to you. One has a cost, the other does not (it could, if you book a candlelight package...).
For her first time to WDW, the party can feel a little overstimulating, even for Disney fans. EVERY sense is overwhlemed, and there is a lot to accomplish in a relatively short amount of time. Lots of fun, super holiday-festive, and you can get in some rides but the time is best spend with unique characters and taking in the specialty shows.
CP is really a quiet, sit-down, lovely show. Regardless of religion, it's just a wonderful show that is bound to stir SOME sort of holiday emotion and fuzzy feeling. There are also festive treats throughout Epcot that are holiday-specific for purchase nearby in Germany or America to nosh on during the show.
Read up on them both and ask your gf what her best pick is! You can't go wrong, they are both wonderful and hard to make a call without knowing you.
Enjoy!