a general rule with water is always look above where you find the leak because water normally always flows down.
the little duct for the ac in the a pillar comes up from below the dash which would make water coming out of it very hard so i would look above it.
do you know if the window has been replaced because sometimes they do not get the seal right and it will leak.
pull the a pillar plastic trim off and soak the outside area where it is leaking and see if you can spot any water inside.