And the "looking very brown" after summer break? Would you say that a black person was looking very brown after a summer?
Honestly, didn't know about that one. That's a stronger case, simply because one might use white to connote fear, or pink to connote embarrassment - she's described that way once or twice as well. Fear and embarrassment are things that can apply to dark skinned people. Tanning is not. (ETA: Well, dark skin can probably technically darken from sun, but it wouldn't be significant enough to spot walking up to the person)
To be honest though, the whole thing is so silly. The original controversy is silly - who cares if a dark skinned person is playing a character that's light skinned! And really that's about as much as JKR should have said. Whether she was correct the actual text allows for the 'Black Hermione' interpretation (which I think the looking very brown quote you mentioned is the nail in the coffin), if she knows she didn't right it that way she shouldn't be playing Twister with it after the fact.
Back to the first quote though (white face), if you assume it was referring to her skin color, what's the point of the adjective in that context at all?