When Merry makes her s'more, the marshmallow is soft and cooked as she squishes the two graham crackers together. In a subsequent shot as she fumbles around with it in her hands just before she is ready to eat it, the marshmallows can be seen as "not cooked" and not soft anymore in being intact and whole instead of melded together.
When Merry and Adam are taking a selfie, they are looking at her cellphone, but the photo on the phone has them looking away.