I think the ballet-like slippers are a great idea! You could make a big deal about them being "Princess" shoes and she will be a "magical, storybook, princess when she has them on". She will probably want to wear them every minute of every day. When my boys were little we would select the shoes that had the "fastest run in them" or the "highest jump". Sounds silly, but you would be surprised at what the power of suggestion can do.
Truth is, in 5 years it won't matter and you will look back and fondly remember her "dislike for shoe phase". Don't stress to much just enjoy her and her unique personality!