Two things -
1) she is definitely a student - no debate here, it's definitely true
2) unfortunately, I confirmed they're doing switcharoo with Sia. I'm sad to say that I went today to see Sia, and was shown to the room with another girl they called Sia. It was not "the" Sia.
I like this place a lot and enjoy how kind they are etc, but I didn't appreciate that at all. I left of course. Hopefully they sort that out. I'd rather get a text saying "sorry, Sia can't make it in today" than trying to pass off someone else as the person I booked with.
So OP, I think this might be why you had the experience of someone who could barely speak English. I think it wasn't Sia after all.