"Sie mag Orangen, oder?"
I don't quite get why 'oder' would be translated as 'doesn't she', so I can only imagine this is a short way of saying a complete sentence like "Does she like oranges or doesn't she like them?" or "She likes oranges or doesn't she like oranges?" or whatever else. If I am right, how would the complete sentence be in German? If I am wrong, would someone please explain me exactly what happens in the sentence? :)
It's the same as if I said in english "You like oranges, no?". They just use the word or.
I think the best translation of this sentence to English would be:
"She likes oranges, right?"
"Oder" literally means "or" in German, however it has the figurative sense of asking for validation. It's the casual way of saying "Correct me if I'm wrong..."
"oder" at the end of a sentence is the German equivalent of the English question tags. The given translation is correct.