I pitch over 500 games with the two seam rise ball .winning over 300 of them,Vdub
the ball moving left or right is soley because of finger pressure. Intentional or not, she is squeezing harder with one side of her hand (or finger), which makes the ball cut in that direction. This can be done with 4 seams, just as easy as 2 seams.
I've heard a pitching coach once say that a 2 seam riseball will move just as much as a 4 seam and I almost threw up in my mouth. This argument is made for the drop also and it's equally as crazy.
Keep in mind, with the way hitters are taught today, mediocre pitchers can get away with things and it makes them look like champions. However, when facing top of the line hitters, they are trying to do 1 of 2 things: Read the pitcher to know the pitch before its thrown. Or if they can't do that, they read the rotation of the pitch to know how it's going to move. In a perfect world, you want your rise to spin as close to backward as you can get. and Your drop to spin forward with 4 seams so out of the pitcher's hand the hitter will have a hard time detecting which direction the ball is spinning. Throwing with 2 seams provides a "looser" rotation and is easier to see for the hitters.
But still, the 2 seam side to side movement is strictly finger pressure. If she works on it consciencely, she will get it and control it and do it at will.