Probably because of the blue dress.

or spring

@Chibi-Chipette: Yeah, a materialistic point of view is not really what these polls about. It's about looking at the Princesses personalities and matching their main emotional traits with one of the four seasons, or alternatively if the character has a special power or fantasy creature heritage then match them with the seasonal representation source of their power. However if you really cannot think of a better reason other than the dress colour or seasonal fashion/looks then that's fine. But I'd rather it be a last resort if yourself, anyone else or myself have run out of ideas/reasons why.

Or Summer.

Her arc is a metaphorical rebirth from wealthy to slave to royal over the course of the movie, and rebirth is usually associated with springtime, so probably this.