During the waxing moon (left one) there’s a doll puzzle. You need to have completed the Coffin Puzzle to get the missing doll to complete this. The goal is to not only line up the style of clothing that matches the doll next to it, you’ll need to line up the hair ribbons as well. So while there are multiple clothing only solutions, there’s only one clothing + hair ribbon solution that I’m aware of. Completing this puzzle will get you another piece of the mirror you need to escape the forest.
Video for this puzzle can be seen here: Doll Puzzle on Youtube
Line up the dolls so that both clothing and hair ribbons match the doll next to it.
When completed, the tree will open and show a new doll. Click on that doll repeatedly until it falls apart into the tree and then take the remaining string. You’ll give that string to Sarah in the mirror one room over. That will produce another broken piece of mirror that you’ll put in the Full Moon starting mirror.