Hi Shelby,
What fun!! A friend recently told me that the on-line Disney store is clearancing LOTS of princesses dresses/accessories that might be helpful in outfitting your princess or providing gifts for friends!
We did a princess tea party for my daughter Mollie's (also adoped at birth!) 3rd birthday. At that time, the Tupperware stand at the Stonebriar mall had a pink, child-sized tea set with Disney Princesses on it. I bought that so that the girls could use something that was easily washable to drink from-- it was a set for 4. We had apple juice instead of tea.
At US Toy Company, I found a small tea sandwich 3-tier tray. I made little tea sandwiches using tiny cookie cutters to make fancy shapes and put them on that tray. Her two little guests dressed as princesses, and we gave them a little purse with some princess jewelry & tiaras inside as gifts.
I have seen at party places on-line those cardboard castles you can buy and color. I found one for less than half at a consignment sale. My daughters had fun coloring it in anticipation of the party, but there was still lots of coloring to be done by the day of the party. As the guests arrived, they helped to color the castle then later played inside it.
Jim Brickman has a lovely CD of the Disney princess songs-- we played that and the girls danced. I also bought a Barbie princess "put the crown on the princess" game at US Toy company and we played that, too.
Mine was a small scale party, but we had a lot of fun. Musical chairs to princess music would be fun. Or, you could have them sit in a circle and pass around a crown or princess doll. "Secretly watch" and whoever is holding the crown/doll when the music stops could choose a prize (such as a piece of jewelry from a treasure chest). You watch so each child gets a turn.
Have lots of fun, and let us know what you do! Fun stuff!
A.