[By the time it becomes apparent that this is indeed the wrong guy, she's already made a fool of herself. The Bakura she had met on the train had a darker complexion, a smug demeanor, and was most definitely female. When he spoke up, her jaw dropped and her face lit up with color as she started trying to sputter out a reply to smooth things over]

Oh! Ha ha ha haaah... I was just kidding. It was a joke?

[It totally hadn't been]

It's Ryou Bakura, right? from Domino High?

[The person she had originally thought was the female Bakura's brother...]

You know- just something to break through those awkward introductions! Since.. er.. you're probably not from the same dimension as me. [No one else had shown up from her version of Domino before so it stood to reason that the trend would continue. Under his gaze the guilt got to her and she fessed up easily] Ok, I might have confused you with someone else. Thief King Bakura... as she so called herself, but it's ok. She's been gone a long time now.