These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Heartwarming Moments: Seeing the girl still visiting her woodland friends no matter what her age is.
The girl's descendant (possibly her granddaughter) having the same ability as she did and plays around the tree in the park. In short, its ending.
Tear Jerker: Seeing the forest practically dead and the tree in the middle of a makeshift dumpsite. Also, the tree only containing a few of the forest spirits meaning that the majority of them are gone too.
The girl is last seen as an old woman dying gently in her sleep surrounded by her family and the giant forest spirit watching nearby.
Prior to that, when the girl was a mother, she seemed to have a habit of trying to get some trees back in the forest since she must have been going there occasionally and planting sprouts. Yet in the end, urbanization still took over and the woman becoming too old, did not have the time to do what she used to do nor would she have to because the city was pretty overwhelming and the forest is gone.