That last video looks so much better. I'd say close attention to trimming as you're doing along with gradual conditioning will work wonders for her. From what I've read, horses bred for big lick potential have lax tendons, and at her age they are even looser. Getting some muscle development will help tighten everything up and keep her from being wobbly.
I agree with
that the hoof angle changes will come slowly as the hoof grows down tighter and you hopefully get more caudal development.
I'm somewhere between
in thoughts about correcting the negative angles. It's somewhat experimental for each horse. As
points out, if you don't bring the landing surface of the heel back far enough, and create the heel buttress platform, those heel walls will keep collapsing and running forward. But also as
says, if you take the heel too low you will never be able to get the tubules in the heel to grow down less angled.
What I've seen is that farriers who believe all you need to do is lift the heel, bring a platform back farther with a shoe, and then the hoof will grow better angles. But they don't trim the toe down enough to make the changes in the angle of the bones, and so the hoof keeps growing the same.
My belief is that you must approach both the toe and heel together. If you can get the horse's weight coming down through the hoof bones, the weight will stop crushing the heel. If radiographs truly show NPA, the horse will have enough sole under the coffin bone to be able to trim some off the toe and take the weight off the rear of the hoof.
If you just try to grow taller heels, it won't change the weight distribution of the hoof. You have to take more toe off than heel for each growth cycle until the weight is distributed better. If you simply take the heels down so the horse has a flat landing area, it won't help since the toe will keep preventing the heel growth.
Imagine in the above xray how massive of a heel wedge would have to be applied in order to correct the coffin bone angle, if you didn't take a lot of toe down. But what you can do is take the toe down some and equally important, get it back to the correct breakover point so the horse can begin to weight through the bones. That alone will begin to encourage the heel to stand up more, and keeping the landing platform of the heel buttress flat as far back as possible will help too. But it will take a long time for that toe correction to begin to help the heel growth, which will in turn help the toe connection grow in tighter and farther back.