Ms. Hui is fluent in English so I don't think that's the problem.
Despite all this, the delay is hard to comprehend. The details that need ironing out cannot be significant if money has changed hands. But if the detais are minor, then there is no reason for it to take more than a few days (it can be done by email almost as efficiently as if everyone were in the same room).
Whatever, we're all speculating. I'm impatient but I am not selling. It will take as long as it takes. When, not if.