>>> Need help with drills to teach daughter how to extend bottom/lead arm extension after contact through ball. She hits with limited power and seems to be pulling off the ball after contact vs. swinging through the ball. Thanks <<<
Although a batter's lead-arm may (or may not) extend after contact, I would question its importance on generating power or ball flight. Keep in mind that the ball is in contact with the bat for about 1/2000 second. During that time, the bat moves forward less than 3/4 of an inch. Once the ball has left the bat, whether the arm extends or not has no effect on the ball's flight.
My problem with drills that would promote the extension of the lead-arm is that it might cause the batter to extend the arm approaching contact. Below is a post (with video) that explains why extending the lead-arm prior to contact impedes the generation of bat speed.
Role of the lead-arm