Actually she is taking 14 steps (alternating legs) all the way through hurdle 7, then she takes 15 steps into hurdles 8, 9, and 10. In her world record you can see she actually has to chop her stride into hurdle 8 in order to do 15 steps and hurdle with her dominant leg...and then takes 15 and hurdles with her dominant leg for the remaining two hurdles as well. I'm sure as she is progressing her and her coach are working on extending the 14 step pattern into hurdles 8 and 9, which would get her back to her dominant leg, and then would allow her to cut down to 15 steps for hurdle 10, again with her dominant leg.
By the looks of her race, it actually seems like she may be able to carry the 14 step pattern through hurdle 9 right now (definitely through hurdle 8). Even if not right now, she's not far off. A little more progress/fitness/speed and she'll be there. Each additional hurdle that she can carry the 14 step pattern through will improve her WR undoubtedly.
As for her 400 flat speed, I'd be interested to see what she could do in the 2 and 4 at the moment. But for her to reach her potential she'd have to focus on both of those events for a decent chunk of time.