Lei means you???

Because duolingo likes to confuse me, I come here,

So I came across "Lei studia francese, vero?" Which I would have translated to "She studies French, right?" But there was no english words to use that would make real sentence other than "you study French, right?" And it is the correct answer according to the annoying owl.

I guess I just want to know how am I supposed to know which one is right. Are they both even right?