Nah, the gold paint per se
is not what supposedly killed her. When the movie was made, a lot of people believed that humans breathe through their pores. Supposedly, covering up your entire skin surface would cause suffocation. Apparently it didn't matter what you covered it with. Bond says something to this effect when she's discovered. I haven't seen the movie in a long time and I can't find the quote.
In the past I had watched the scene any number of times without paying attention to the dialogue. My assumption was that Goldfinger had simply encased her mouth and nose (along with everything else) in some sort of quick-hardening gold solution (referred to as "paint" for simplicity), and she suffocated the normal way.
These days I take it he did not
close off her airway with the gold; otherwise, this skin myth wouldn't have come up.