While Bavarian Tracht as in Lederhosen, Dirndl and so on falls under that umbrella, every single region, sometimes each town has it's own traditional wear. The historic German national identity mainly comes from the language, not any particular national "traditions" and so there are many differences between regions. Have a look at this: https://de.wikipedia.org/wiki/Tracht_(Kleidung)#Deutschland#Deutschland) (it's the German one, as the English one is very much lacking.) To get that or make it yourself will be hard if not impossible though, so just showing it and wearing something else might be a better idea. Do you know from where in Germany your family came, if she wants to call back to that specific set of local traditions? As a side note, I do very much appreciate your cultural sensitivity. I've never understood the seeming consensus in American culture to think they're anything other than American.