Do you mean the kind that the shape is made out of wire and is covered with nylon? Kind of like the fairy wings that you see a Halloween time? If so, get a large piece of paper and make a template. Then shape wire according to the template. As for the nylon either buy tights/pantyhose in the colors you want or buy plain cheap pantyhose and spray paint them in the colors that you want. Then slip the nylons over the shaped "wings". For the center buy some coordinating fabric to make the body and attach the wings to the underside of the body.

Lavender is a great color but. . . I have a friend who did her DDs room lavender. At 1st her DD loved it but then found that the color was making her feel sad and depressed. Also her DS has Asperger's and would get agitated if he spent too much time in the room. I am not sure if the agitation was caused by the color or by his sister. lol Anyhow, they just repainted her room a couple of weekends ago. The shade of lavender could have been the issue. A deeper purple could do that while a softer more pale lavender would be fine.

Yellow is a bright cheery color. It brings warmth and happiness in to the space but can be stimulating as well.

Another suggestion, if you are going to use soft/pastel type colors, buy some top sheets in a couple of colors that she likes. Then tack them on the wall (at separate times, not all at once) and see how she reacts over time to each of the colors. By doing this, you will be able to see how she is around each color. The color that is most soothing to her and creates calmness within her is the color I would paint the room. The bonus, she will have coordinating top sheets once the room is painted.