I have included a link to a previous question similar to this, answered extremely well on enotes. Sae's experience of being violated in terms of her trust and her openness at the hands of a criminal has an irreparable impact on her psyche and her perception of the world. From someone who was open and trusting, the experience transformed her to doubt this, and to be skeptical of it. In the end, the garden allows her to interact with something in the world and step out of the shell caused by the incident. In the action of gardening, there is caring for something outside of self, trust in the world, and faith that human action can be geared towards good. It is precisely the care for the garden that becomes therapeutic, and helps play a vital role in Sae overcoming the pain she experienced and the trust that had been violated. It is another example of how the garden is able to present a vision to someone from what is into what can be. This transformative power of the garden is something that Sae ends up relying upon as she plants and nourishes not only the garden, but her own sense of self.