I extracted the birthday girl from two different photos and placed her on the layout on the layer directly above the purple background. With the extraction layer highlighted, I chose "Luminosity" from the drop down menu at the top left of the Layers Palette.
This worked great for the top extraction, but looked strange for the bottom extraction because the top of the birthday girl's head was below the color photos. In Photoshop, I made the bottom extraction it's own layer, pressed "Ctrl" and clicked on the layer to get the marching ants around the extraction, then I highlighted the color photo layer and pressed "Ctrl" and "X" to crop the color photo around the extraction.
