Unlike the bad witch character from The Wizard Of Oz, Glinda is a good witch and dresses in pretty pastels. Her gown is pink and shimmery, and her tall crown really makes her stand out. The crown is made up of silvery sparkles and glitter. Making your own Glinda costume isn't hard, but you may have to spend some extra time to create a crown worthy of the dress.
Fold the Mylar sheeting around the head of whoever is going to wear the crown so you can gauge how long the crown will need to be. Leave a little extra space so there will be room to put the crown together. Cut off the excess Mylar.
Lay the remaining Mylar on the work surface. Using a pencil, sketch how you want the crown to look. Glinda's crown in the movie is quite tall and has six star points around the top. You can interpret the crown however you desire. The suggested height of the crown is relative to the wearer, but for an adult it should be about 12 inches high, and a small child's should be about 6 inches high.
Cut the crown out, being careful when cutting around any detailed points and areas.
Decorate your crown. Glue a rhinestone to every point of the crown, and outline the crown in glitter glue. Brush silver glitter onto the entire crown with a paintbrush. Add a lot of sparkly detail to the bottom centre of the front of the crown. Allow the entire crown to dry before proceeding.
Staple the crown together at the back, using enough staples to keep it in place, but making it loose enough so the wearer can easily slide the crown on top of her head.
If you don't want to use plastic Mylar, or if the points are too heavy to stand, back the Mylar with poster board or make the crown from silver poster board instead. Look at a photo of Glinda for reference, or watch the movie to copy her look.