It's been a while since I have been in Munich, but when you step out of Terminal 2 you are indeed in a large area between Terminal 2 and Terminal 1. There is a Biergarden, but there are also some other restaurants and shops. Downstairs between the two terminals - where the train station is - there is also shops and some restaurants, as well as a Supermarket.
Depending on her arrival time, maybe some local traveller could recommend some place where she could have a nice breakfast and some wifi i.e.

If she likes watching planes she could also go the "Besucherhügel", which is a viewing platform. Or maybe make an airport tour... Nice to pass time and somehow interesting...

Other than that I don't really know what else can be done, as there is not much nearby in MUC since the airport is really remote.