I've never been to Florida before but my sister had a makeover at the DLH last year.
You have to go to the shop at the DLH to book your slot. Do this as soon as you arrive so you have the best chance of getting the day / slot you want.
On the day you take your daughter to the makeover station on the first floor dressed in her princess dress and they do her hair and makeup and if you want them they take photos afterwards.
My sister enjoyed it and most reviews I've seen are positive however I have read a few on Tripadvisor where people said they had been disappointed. One lady said it did not compare with the service at Bibbity Bobbity Boutique in Florida - she said the CM who did the makeover did not interact with her daughter at all. That wasn't our experience but as the shop manager was there with us that day I don't know how typical our makeover was.
Have a look at some reviews - search for princess for a day or princess makeover - then you can decide for yourself.