Why is this not right?
When asked to translate: Der Apfel ist fur Sie, I translated it as: The apple is for her. However, it rejected that, and said the correct answer is: "the apple is for you." My question is, what makes my answer wrong? Doesn't Sie also mean her?
Not if it's capitalised. sie (not capitalised) = she/they; Sie (capitalised) = formal you
It's because it is at the end of the sentence yet capitalized. If it were at the beginning of sentence it could be "she" but because it's capitalized at the end of the sentence it has to be "You". I hope that makes sense.
"Sie" is used in formal situation, maybe a formal letter or talking to someone you just met ...."Du" is used when you are with friends, family...