I just modified it a bit for Princess Anna. She has a separate tutorial for Anna's dress, but I cheated and used a second, black t-shirt and cut the sleeves off. I kept the blue t-shirt separate (they can still wear that everyday!) and attached the black shirt to the skirt like the Elsa dress.
I found everything at Walmart except the gold bias tape (Hobby Lobby) Surprisingly, Hobby Lobby and Joann's were total duds when it came to fabric. The shirts were around $4 each, the snowflake fabric was in the clearance bin, and most of the yardage was $2. I had the green ribbon and pink for the flowers in my stash. Even the snowflakes were in Walmart's Christmas section.
For the Anna cape, I took a length of fleece long enough for a cape plus the shoulder drape and marked where the drape and cape would "meet" with pins. I then attached a length of elastic a little bit longer than shoulder-width and gathered the fleece by stretching the elastic and sewing a straight line from one end to the other. I attached a couple of ties, folded the shoulder drape over the elastic to hide it, and, voila! The fleece doesn't fray and this color from Walmart was PERFECT!
Two Anna dresses were an easy sew today in between laundry and dishes and Gilmore Girls. It helped to have it all cut out and pinned, which I did after bedtime last night. The Elsa dresses took a day, as well. I do have a few hems left to sew after we had a fitting.
I did make two Elsas and two Annas because two of everything is required in this household. It's like having twins. Kinda sorta.
You can do this! The hardest part is the gold bias tape, but it makes the dress. You could totally do gold ribbon instead and use a black tank so you don't have to worry about covering the edges (I couldn't find one my girls sizes).
Now, the challenge is to make sure the younger copy-cat is ok with being Anna on the big night!