Advice to a coach who wanted to know how to coach a girl in getting a quicker release:
To get a quicker release, all you need is an intention to catch more of the leg drive energy and put it into the shot.
As one goes to jump, the knees are bent and then straightened as the lower and middle parts of the body generate power. As this "upward" force is happening, the most force is available at the beginning, and then it dissipates as the jump occurs. You could say there is 100% of the force available at the start of the jump and zero % available at the top of the jump.
Many players wait to shoot until late in the jump, I guess so they can elevate a bit to prevent the shot from being blocked. I know a lot of coaches advocate shooting "at the top of the jump."
But, to me, you want that upward energy created by the lower/middle parts of the body to power and stabilize shooting! This is for most shots, including free throws, and especially for threes. There is a place for shooting at the top of the jump, but it's relegated mostly to the bigger players who are doing turnaround shots from in close and need to elevate to prevent a shot from being blocked. There, the margin for error is big, so the stabilization factor of the legs is less needed.
To set this learning up, ask your player to jump up and down and feel the power of the leg drive or leg lift (whatever you call it). Have her do a big jump and a small jump and a middle sized jump. Describe to her and then have her feel what 100% of the force feels like (whatever size she decides to create) and what zero % feels like and different percentages in between. Then ask her to take a shot and tell you what percentage of the available leg power she used. (Note this is not how "big" the force is, just what "percentage" is utilized.) Let's say she says, "50%." Then suggest she shoot from a higher and higher percentage and tell you what happens, what it feels like.
She will start reporting that the higher the percent, the quicker the release, the higher the shots, and the more "effortless" they feel. This is one of the key ways to improve shooting.
Now she's into learning, and she can do it a lot on her own. The awareness and feedback of this approach lead her to discover for herself what works best, and it will surely be to shoot quicker from more of the upward, leg-driven energy.