Translation:You don't need to introduce us. I know her.
Yes, Chinese often omits subjects and objects where they must be included in English. "You don't need to introduce" is not a complete sentence in English. "Her" or "me" could also be correct, but as we do not know the context, a more general "us" is probably best.
I wrote "her" and it was marked incorrect. So write "us"! Learn from my mistake!
It's not your mistake, it's a mistake in this course, which is a beta course, and we're here to improve it while it's in beta by reporting omissions like this to the Duolingo team.
This should accept "... introduce us", "... introduce me", and "... introduce her". They're all accurate translations and all perfectly natural English.
I answered as below - but was failed for using the male gender pronoun instead of female. Given that 他 and 她 are homophones, how was I supposed to know the female was required?
You're right, for the listening module "他" should be accepted, but for all the others just "她".
It should be You don't need to introduce us, I already know her, because the period is unnecessary and it 我认识她 means I already know her
It sounds very unrealistic (the English.) You would replace us with yourself/him/her. Us doesn't sound right.
As a native American English speaker, I disagree. "Introduce us" is perfectly natural.