Have you considered looking into using felt, and then needle felting roving into place to give it a more fluffy texture? It would be way time consuming, and would essentially ask that you learn a secondary craft... But look up some tutorials - it may give you the look you want? I know I've seen some pretty fluffy things come out of different felting techniques.
I can't say I've seen a fabric that will do that naturally, just from long fibers, and still look good - not like a stuffed animal that has had the fluff loved out of them... The minky may be your best bet - it does have a plush, soft look - maybe not cotton candy, exactly, but it would still have a fluff to it?
Party Pirate Pinkie Pie (MLP:FiM) 100%
Eris Discordia (MLP:FiM) 100%
Convention Line-Up: BronyCon 2013 - Dragon*Con 2013
Eris (Female Discord, MLP:FiM), Casual Gala Pinkie Pie (MLP:FiM)
The 10th Doctor, blue suit variation (DW), Queen Mab's Party Dress (Dresden Files: Cold Days), Party Pirate Pinke Pie