Not to muddy the waters, but a lot of the high level TB teams in CA are now teaching their infielders to stay down on the ball and throw sidearm, especially MIF. If your DD does not have accuracy issues throwing side arm, I would not fix it. Most coaches teach over the top throwing motions because up/down throwing issues are more easily corrected than left/right, but staying down on the ball and throwing side arm saves time when you are facing fast slappers and bunters.
I think one thing that is missed in the sidearm action is whether or not the head is moving with the arm slot. Your head shouldn't be in the same position when throwing sidearm as you would when you are throwing over the top. The distance between your head and hand shouldn't be any different if you are throwing over-the-top or sidearm.