That's still argument from authority, like saying "Colin Powell is known to be a highly educated man and honored soldier, how could he be possibly fooled by faked documents?"
there is the possibility that the anonymous blogger has just as much integrity and honesty as pg. We don't know whether or not she does. We do know what both parties have said in public. therefore, we need to limit our evaluations to that until further information is known.
What about in the other direction? I have no information about the author's credibility whatsoever, but from personal interaction I have ample information about PG's credibility.