Tom, I think you’ve got a good athlete there with a fine flowing style. Very nice to watch. She’s got a pronounced forward lean, but then so did Sally Gunnell. And, also like Gunnell, she has a high back-kick. The two things usually go together. What you see from the side-on shot is not something I’d worry about.
More worrisome is what you see head-on. There’s a noticeable lack of symmetry, suggesting to me a chronic pelvic twist.
You’re talking about her renegade right foot. Well, it doesn’t rotate on ground contact, it’s heavily pronated before it hits the ground. And it looks worse from the back than from the front. I managed to freeze the clip in a couple of places where I found the foot grounded at an angle of 30-40 degrees off true. That’s heavy pronation.
Then look at the arms. The right arm going back shows about a foot of daylight between it and the trunk, whereas the left stays quite close in. This is not an arm fault as such, but simply the necessary compensating manoeuvre for imbalanced action elsewhere. To me, what it all adds up to is maladjustment in the pelvis. If you could cure that, the unbalanced arms and the pronated foot would most likely correct themselves.
How would you do that? Well, not in the gymnasium. It’s a job for Frederick Matthias Alexander. Google for the “Alexander Technique”, and take it from there. But you (and she) might have to decide whether to take the drastic step of giving up running altogether until it’s fixed. Because the problem is that this is not a matter of accidental misshaping, it’s a matter of faulty usage of the muscles generally, probably dating back to childhood. She will have to retrain them. And running, especially when heavy training is involved, can only inhibit progress by emphasizing old habits while she’s trying to build new ones. You see the problem?
If that seems like a retrograde step, I would suggest that it might be worth the investment. I always wince when I hear someone describing lopsided body action as a “personal idiosyncrasy”. It’s not that at all. It’s plain wrong, and it can only slow you down, especially in sprinting where mechanical imbalances have a much bigger effect than they do in distance running. If you have a wobbly crankshaft in your car, you probably won’t notice it at 30mph - but you’ll notice it at 60. Not only is it having a detrimental effect on all the other moving parts, it’s also setting a limit on speed. If you can get your girl to run symmetrically, she’ll run faster.
Good luck anyway
Pat