This is the simplest dance, the Glide Waltz, being done by a very assured and graceful young girl, amongst a lot of assured and graceful young girls. I was doing this yesterday–not in a sparkly dress and not quite as assuredly.
You hear her coach count for her and tell her to push. One of the secrets of these dances is that to look graceful, you have to go far on each step and to go far, you have to push off hard. Power + balance = grace.