ODPOWIEDZ! - Deutsch

Głosuj teraz!Bez odpowiedzi
Sie sind ein Mädchen?

Can I say "Sie sind ein Mädchen" if I intend to say 'she is a girl'? Wouldn't the translation be litetally 'They are a girl'? 

I mean, on Duolingo they have put this way and I can't realise why. Please, could anyone explain me?