Translation:She is my classmate in Chinese class.
No she is my chinese classmate would imply chinese as a race and hence does not translate
Translation choices are context dependent - we aren't given enough info here to say "She is my Chinese classmate" is wrong. If I were introducing someone who was not ethnically Chinese and said "She is my Chinese classmate", people would assume we study Chinese together. Just like if you said "She's my French classmate" or "She's my biology classmate". A native speaker would try to avoid saying class twice - "Chinese class classmate" sounds awkward.
That isn't technically true, but it does make the sentence ambiguous in English.
I would say that "She is my Chinese class classmate" should be accepted
How about: "She is in my Chinese class"? This wording fixes the redundancies, and its meaning is clear and unambiguous, I think.
"she is my chinese classmate" was disallowed. I realise this is potentially ambiguous, but in context this would be fine
I agree that in English at least, this sentence is grammatical and would be used in conversation, which in turn would have provided the context that diminishes the ambiguity.
To avoid ambiguities, I'd say, "She is my Chinese language classmate" but this is a bit awkward. Most English speakers would say, "She's in my Chinese class." Although it's not a literal translation, it's the most natural one
In order to make the English sentence sound natural I think it's necessary to rearrange it a bit so it's less literal. I would say something like "She is in my class for Chinese" or "She is in my Chinese class" - though obviously Duolingo doesn't accept this and never will. Just for the record though.
'She is my classmate from the Chinese class' is a little clumsy, but should be accepted; it was corrected to '(...) from my Chinese class'. I don't think the 'my' is quite necessary there, it comes out from the meaning in both English and Chinese sentences. The sentence kinda logically implies that it's my Chinese class in either case, with 'my' or without it.
Just thinking about this context: where is your headmistress? She is in my Chinese class, so she is not my classmate.
What's the head mistress got to do with anything? She's probably in her office doing admin work rather than actually teaching anything!
The teacher is in the classroom, but no native speaker would interpret "she's in my class" as referring to the teacher, because if you did mean the teacher you'd say "she teaches my class".