It's not that her brain does no interpolation, it's that part of what's being interpolated is changes that happen to the magic that's already in place, and power that flows out of Opalyn without it quite feeling like the same sort of thing as moving your hands, and she can feel it happening but that doesn't mean she gets all the details on what's happening any more than you know in numbers how fast your hand is moving when it moves--
Anyways, the ball of sorcery does something that actually looks more than slightly unnatural, as if you threw a basketball and then it didn't move quite the way Newton said it should, and ends up matching the target ball pretty well, so far as intensity is concerned.
The weave is still too far apart, though.