Have you thought about a healing project or on-going activity, that would include you and your daughter and the recovering girl and her mom? Something that is special and can last the summer. Maybe a pick-a-park-picnic where every week, the girls pick a different park and the four of you have a picnic there? Talk it over with the mom and see if you can help strengthen the girls' friendship and everyone can recover from this nightmare.
Go ahead and make a healing/comforting quilt but this will take time to make. It will help you heal as you make it and the girl will love it when it is completed.