Why not make it of things she loved as a child? Reminders of things like that could very well bring back happy, wonderful memories for her. Add in some things you fought over as sisters maybe, or fabrics of things to remind her of things you did together? My sister and I used to fight over doing the dishes, so I'd include some fabric like that. It's what I would do if she was my sister!
My prayers are with both of you.
