Super Trooper,
My wife attended the " Cocktail Party ", is it an interview or not. I'd say no, however, it payed off for us that when she was cornered so to speak, that she had an answer for the questions she was asked.
Where will you live.
When will you join your husband
What about schools
Do you know anyone already here
It also helped that she also had studied the local political situation in HK, do you know that under laws passed last year that as a spouse she can no longer get a work visa, so what are you going to do month in month out now that you are unable to work.
It might not be an interview, but it will help a great deal if she has put some time and effort into the " whole interview " process, and of course, all the rest, don't drink too much ect, ect. Good luck.