Griz, if the girl is only watching the hip, then she is cheating herself out of very valuable information that would make her a more successful hitter. The pitcher can give away many clues as to what she is throwing before the ball even reaches the hip. I've seen girls who can give away their grip on the ball based upon the amount of time it takes to grip the ball from one pitch to another. The muscle movement in the forearm can disclose a pitch grip. What's even more important is that some players can actually follow the ball around and see the grip on the ball before it's thrown. The pitchers arm circle is also a great timing device for the batter. Yes at some point the batter needs to focus on the hip but not at the expense of all the other great clues that may be revealed by the pitcher.
I once had a long discussion with Crystl Bustos about this very subject. She spends a great amount of time in the dugout looking for signs where the pitcher reveals pitches before she even gets to bat. I even had a conversation with Dot Richardson about the first time the Olympic team faced a young 16 year old pitcher that was striking them out. After the first time through the lineup, the entire team was sitting on the dugout steps watching every move this pitcher made in hopes of picking up a pitch clue. That young pitchers name was Cat Osterman, who eventually joined many of those players as an Olympian.