Hard to say for sure without seeing video of your swing, but sounds like she was on to something. Good chance that you were trying to get extension too early and ended up casting your hands, resulting in a looping swing and/or dragging the bat through the zone. I had to adjust a lot when going from hardball to softball, but I learned that a smooth, compact swing will generate plenty enough power. Usually when I am "off" it is because i start trying to put too much into the swing and my hands drift. Try not to overthink it. I usually just make sure when I load that my hands are in tight, just above my shoulder, then make sure they fire inside the ball. I trust that everything else will work as it is supposed to as long as I make sure to take the quickest route to the ball.