I began by gaining inspiration from animations that use 360 spins, such as Disney films, with the main princess/character spins to show off their dress or simply dancing much like the classic scene in the animation film Beauty and the Beast.
With the character spin, the animation takes into consideration the 12 disciplines, such as follow through, pose to pose, anticipation, arcs and emphasis. Using emphasis with in the spin, gives that classic Disney feel with the stretch of the arms and the movement of the hair and dress that follow the main action of the spin. This can be seen in the Sleeping Beauty line test of Aurora spinning as she talks to another character.
In the Ariel gif, I can see that the movement of her character would involve elongated and stretched anatomy and facial features for it to smoothly work.