There's a difference between non-Chinese characters who are swearing in mangled Mandarin (as it's clearly not their first language) and a supposed speaks-Chinese-only girl who actually doesn't. I wonder, is it really that difficult to find an Asian actress who actually speaks Cantonese (or Mandarin, they could have easily switched dialects for the script), for such a (presumably) minor part?
And Buffy really didn't know what to think of Wood. But she trusted him more than she didn't.
As I said, these are minor quibbles. But true craftsmanship, in any form of art, is in the details. Details make or break the final product.