feline fanatic

I really like the idea of including signatures and messages from the troop. That would hold so much meaning for her and hopefully many happy memories. At the stage the quilt is in, it will be easier to do it on the back. This way you can iron freezer paper onto the back of the fabric (to stabilize it for drawing/writing) and you could give each girl in the troop their own square to do whatever. This way no one can complain, hey she took up more room than me, or she copied what I did. If you give each girl a 10" square and some sort of permanent fabric paint/or marker and let them go to town. Additionally if one girl misses the meeting where you do this, they will still have an opportunity to participate. Also you can involve the troop leader. Tell her you want to make a quilt for memory, she will never guess it will be the back of HER quilt.
Your other ideas for the white squares are fabulous. I really like the idea of quilting in the GS symbol but other applique would look nice as well. You already have vests with badges and of course the cookies (my two faves, thin mints and samoas!). What about activites that the troop had done? Like did they go camping you can do a tent with a campfire. Did they do any special trips? Maybe something to signify the trip. Or maybe you can find out if she has some favorite things. Like maybe a favorite flower, or she is a cat bird or dog enthusiast. Does she like to cook or bake? You could a rolling pin and chefs hat. If you could add a few personal touches by trying to find out if she has favorite hobbies you could somehow depict those in the squares signifying interests outside of GS.