Ok, after checking out the vid, it looks like it was done using a combo of 2 techniques: Softbodies, AND paint effects.
It looks to me like the braided parts were a custom "braid" PFX brush attached to a softbody-curve. Pretty simple dynamics.
and...
The flowing hair looks like a clever usage of VERY WELL TEXTURED strips of softbody nurbs and/or poly geometry.
Add fan, turbulence and gravity fields to all, and you have some sexy hair effects for that shot!
Keep in mind, the "hero" or close-up shot of her hair only lasted for a MAX of I would say about 30 frames or about 1 full second or so, but still, give it up to Square, they are good!
Israel "Izzy" Long
Motion and Title Design for Broadcast-Film-DS
izzylong.com