What is considered appropriate women's attire for a PhD interview in Germany?
I think this is highly field dependent, but in general overdressed is better than underdressed. In fields close to mine (math, computer science) things are quite relaxed, so no one would expect a (skirt) suit (although this would be ok) and nice trousers (usually including jeans) and shirt are most probably ok. Ragged jeans and t-shirt may not always work, though. Avoid wearing something revealing.