this translation seems very far away from the german one...

I think, the correct translation would be "Did you happen to meet her?"

The German looks like it is a mis-translation of the Japanese.

Actually it's more like "By any chance have you met her?". ひょっとして indicates a fairly far-flung speculation on the part of the speaker.

Yeah, that's what "zufälligerweise" expresses.
But does the above English sentence have the same meaning as your translation? "Do you mean you met her." rather sounds like "Come on, you didn't meet her, did you?"

> "Do you mean you met her." rather sounds like "Come on,
> you didn't meet her, did you?"

It doesn't sound that similar to me.

> Yeah, that's what "zufälligerweise" expresses.

The final の is also significant. In this case I think it indicates an 'explanatory' sense to the sentence. In other words, it the person spoken to has met her it explains something (that they've just said, for example).

An alternative translation for the Japanese might be:

"Could it be that you've met her?"