My DD throws a 2-seam and a 4-seam fastball. The 2-seam has a screwball "tail" at the end that makes it a very effective pitch if she can located it. Her 4-seam is more of a corkscrew spin that we only throw on a three ball count to a batter we would rather put the ball in play vs. walking.
I would have to assume she's got a feathered release action or possibly a touch late release if shes getting corkscrew action. (ball isn't coming off 3 fingers evenly?) This "flaw" can absolutely be effective and may or may not want to be addressed. It may become a bit difficult in hitting low and out if the ball is cutting back in towards the sweet spot? That's just my mind spinning on that pitch. thanks, James