I'm going to have to say that the best option isn't listed here. "Knew" is past-tense; it doesn't match the present tense of "talks". "Knows" is what I would use.
Thanks for the help, Julimaruchan and joadbres.
I know that American people usually use "as if she knows ..." etc... But to my knowlege, you can use the subjunctive mood after "as if".
a. She talks about him as if she knows him personally.
b. She talks about him as if she knew him personally.
c. She talks about him as if she had known him personally.
(b) is on the weak side, but I'm sure I've heard it, and probably have even said something like that myself.
Yes, you are absolutely correct. "Knew" is not past tense here, but subjunctive.
But knowledge of and use of the subjunctive mood is gradually being lost, as you can tell by the others posting here who view the most correct answer as substandard English.
I disagree. 30-50 years ago I "knew" people in my high school, in the army, and so on, that I've long since lost contact with. Now, I might say that I knew them, but to now say that I know them would be a misrepresentation.
Or, let's say I had known this guy named Rob Porter for years, but have recently heard something surprising about him. A few weeks ago I would've said, "Yes, I know him," but now...?
I disagree. I see no difference in (a) or (b). I wouldn't ever use (c), so see no point in comparing that to anything else.
As for my comment about always knowing someone, I am referring specifically to the expression at hand, used in the original sentences: know someone personally. It is unnatural to say something like "I used to know her personally, but now I no longer know her personally." Once you know someone personally, you always do. You may not have met them in a long time, but that doesn't change the fact that you know them personally.
"I used to know her personally, but now I no longer know her personally." Once you know someone personally, you always do. You may not have met them in a long time, but that doesn't change the fact that you know them personally.