To be honest with you, I know almost nothing about training for anything longer than 400. On my 4X400 relay teams I occasionally have an 800-type runner, simply because she is one of the 4 best on our squad. Her training is up to her distance coach. I will try to get a bit of speed into her, but basically I have to take what she brings.
I believe that all pre-high school runners should sprint. But my observation over the years is that young athletes who switch to distance running in high school have the speed trained out of them by their high school coaches. They become plodders. Speed always matters, in my opinion, and you must continue to train it.
As for special endurance, this is a complicated and controversial subject for young runners. Look at
https://www.charliefrancis.com/community/showthread.php?t=7593. This thread is almost unbelievably long, and it will take you many, many days to read it all, but it is very thoughtprovoking and I think you will find it useful.
Is the athlete your daughter?