I'm making an AUTHENTIC princess dress for my little cousin. HELP!!!! I need ideas!!!!!

I am currently not a member of this club but I was hoping that you all could help.

What do you think is the prettiest princess dress? My little cousin likes the really puffy dresses, the color blue, and she currently got a Little Mermaid Vanity for Christmas. But her favorites are Anastasia, (and totally unrelated) TinkerBell. I know that technically they are all similar but which do you think would look prettiest on a cute, little, short, three-year-old girl.

Honestly, I think Ariel's pink dress is the prettiest, but I could make it blue. Also since it is still winter I am also planning to make her a cute little cloak.