You were French and you were Sirius' sister, you know how to speak english very well, you don't even have a accent, but you were lost now, you enter Grimmauld place because you wanted to found someone to help you.

You were visiting with your wand on the Lumos spell as you enter a living room and you see a man sleeping, he seem sick, he got some scars on his face.. you recognize him as you old bestfriend Remus, you were a Marauder.

So you quickly put your wand away but, even if you were a witch, you were kind of lost here, because you never really saw Gringotts or at least not that place.