Hips leading the swing is correct. This guy will tell you the same thing...
https://www.youtube.com/watch?v=4ZgBZzqhvxkIf the hands and/or shoulders are moving forward before the rear hip, it's a pushing swing, and not what happens in the pattern of high-level hitters.
The hip pulls the shoulders, which pull the hands, which whip the barrel through contact...
The big part of the equation is getting rid of the slop/slack in the connection between hip and hands, which can be challenging for long, lean, flexible young girls to feel and execute. Another important part of the equation is proper hand use. The hands are the pivot point for the rotation of the bat, rather than the arms swinging the bat around the spine.
This is my favorite example to show the hand pivot point...
An important thing to notice is that the hands stay connected to the movement of the rear shoulder early in the swing, pivoting the bat to the plane of the pitch, until the bat is whipped by the hands through contact. The hands do not loop around the body, they move in a short path out from the rear shoulder.