Start by making a pony in the middle of her head, leaving the edges out all the way around. On the last pull through the elastic, only pull halfway through. (This part isn't shown, but since my daughter's hair is so long, I pulled the bottom part up and brought it back through the elastic to make the bun, if your daughters hair is short enough for one pull through, leave the ends out on the top instead of the bottom.)
Start parting out a section of hair and twist the heck out of it, adding the twisted piece to the bun.
Go all the way around her head. With the extra ends you will have from the twisted pieces on the bottom, twist them together and wrap them around the initial elastic.
Piece and spread everything you have left, to make a messy bun.