She must be near the water of the fairy gate at all times. We must find a way to make it portable.
1 - Something to store the water in. 2 - A way to access the water. 3 - Something that will hold the container. 4 - Something that will seal the container.
One that the fairy would approve of; it should come from the forest, or one of its critters.
You may need to exit the tree hollow.
Return to the cage outside and take the snail shell from it. This should do a good job of holding the water.
Come on, it's a point-and-click adventure game. The protagonist's arms are never THAT long.
You need a way to make the water flow closer to your level - it may require a hard whack.
Use the hammer in your inventory on the 'brittle spot' of the fairy gate.
A piece of material that could be comfortably worn around the neck.
You won't need to exit the tree hollow.
Grab a leather ribbon from the rock on the right.
Again, something forest-y. It needs to be small enough to fit in the hole and plug it completely.
You won't need to move.
Use the acorn in your inventory to seal the shell after combining its other pieces.
Give the finished creation to the fairy, and show her the wonders of modern civilisation! Oh boy.