Things may have changed since we were there in Sept, but my dd4 loves princesses too so here is some princess stuff for you to do:
MK - Storytime with Belle - runs many times a day. Belle reads the B&TB story to the audience & picks audience members to help. If your friend asks the CM she can probably be in it. You have to be assertive!! Cindy's Surprise Celebration out in front of the castle - also runs many times a day. It is awesome & features MANY princesses & princes as well as other well known characters. Cinderella's carousel - in Fantasyland. Ariel's Grotto - Little Mermaid hangs out here. Toontown - There was an entire room with princesses doing meet & greets. I think it was across from Donalds Boat but you can ask a CM. The parades feature princesses, as does Wishes to an extent (Tink flies off the castle).
EPCOT - PSB in Norway was great but hard to get in to. BUT all the princesses were in their respective countries & NO ONE Was around them so we had tons of interaction with them. The times guide even lists when certain characters will be in their countries. I also saw a lot of vendors selling make your own crown stuff.
MGM - Fantasmic features princesses. B&TB show is awesome, as is VotLM.
AK - My dd feels Pocohontas is a princess so she likes the Animal show (to me it is boring). If you really stretch the whole princess theme I guess you can say Princess Atta is a princess & watch ITTBAB too!!
My dd got a bunch of pins to trade for all princess pins which was really fun! Dh & I got in to pin trading too. We came home with 16 princess pins!!! And some penny presses feature princess too. We also made sure to get pics & autographs of all the princesses we saw. It is very cute to see how they sign their names!!!
If you go to Harmony Barber Shop they can put pixie dust in your hair so you feel like a princess!!
DD got lots of t-shirts that had princess characters on them that she wore daily!! It was too hot to wear her real costumes so that was the next best thing! Oh yeah, she also had a name badge from laughingplacestore.com that had princesses on it & her name engraved on it so everyone called her Princess Abby!!
That is all I can think of right now. Hope this helps!!