"You are a girl."
Also, it seems to me that вы is used when you're speaking to someone in higher stature then you are. ты when someone is lower then you are. In this case is it a girl, not a woman. Which, I think is the reason that it is used in this case. Can a Russian speaker back me up/correct me?
From what I get, the Russian "о" lies somewhere between English "uh" (like in "unlike") and "o" (like in "or") and can oscillate between the two sounds, which is probably the reason for the different transcriptions. The tips on this lesson try to clarify the pronunciation a bit.