One thing I picked up from this video is that I have never heard a coach spell it out to the infielders that they 3 seconds to get that ball to 1B for the out.
And out fielders, assuming play is still at second have approx 5 seconds to get the ball to 2B for the out.
so.... that being said.. is it wise to teach the girls to "step & throw"?
You do teach step and throw but maybe not like you think. The step is done when transitioning from fielding the ball to throwing. So you don't field the ball, stand up, step and throw. It is all one quick motion. There are also times when you do not step when you throw. There are many variables: the kids arm strength, where they are when they field ball, how hat the ball came off the bat, the speed of the runner, which position, ..... But for young kids they are taught to step and throw. Here is a good video that shows the footwork for different throws.