I am in Germany and have a German girlfriend. Where is an inexpensive place to vacation?

How about Malta? Bed, breakfast and flight for one week should be around 500.- Euro each, if you are lucky less, and you are there in about 2 hours. You find several nice places, nightlife, not much stress, some interesting landscape (e.g. Dingli cliffs, the highes cliffs in Europe), a well working infrastructure (including an excellent bus system), a lot of culture, friendly people but not many animals. Malta is good for diving but not for swimming. Another advantage is the language, besides Maltese English is second official language. Nightlife is in St. Julians, I suggest you take a hotel there or in Sliema. Avoid hotels too far away from Valetta, Sliema and St. Julians as the life is there.

Lake constance is really nice. I'm from America & I was just there. I kbow you said she doesnt want to go in germany, but Its on the border or Switzerland & Austria so you can spend time in the Swiss alps without having to travel too far from germany. I'm not sure if you've heard of it, but its a gorgeous lake. There's lots to so since its a tourist site. You can take boats around the lake, go to the islands, or visit the historic buildings in the area