How does the development of Melinda's art reflect her process of healing and recovering?

Melinda is portrayed as a rape victim who is so badly traumatized that she can barely speak. She also can barely look at her own image, and puts a poster of Maya Angelou--who famously was silent for years after enduring abuse--over the mirror.
While Melinda is absorbed in art, she would rather choose the circumstances of its creation. The art teacher does not allow her to do so and insists that she, like all the other students, follow the rule he laid down.
For a long time, she resists this restriction, making art that does not match her true inner self. She tries to keep her own, genuine creativity separate from the school assignments.
Melinda's ongoing battle with PSTD, with which she seems to get little support from her parents, escalates until December. She is moved by their gift of art supplies, which shows that they understand something important about her.
The art teacher is also trying to reach her. The tide turns when she discovers Cubism, as she realizes that understanding meaning does not require attempting realist-type verisimilitude but is concerned with what is beneath the surface. She starts to channel her creativity into the school project.
With the spring, time of renewal, she and her creative tree grow together. She is not as tormented by the surfaces of things but can reach inside for what is meaningful to her. She extends herself, first anonymously, with the graffiti warning other girls about Andy. She continues by directly warning her friend Rachel, despite the risk of disbelief.
Melinda slowly recovers her spoken voice as she gains her artistic voice.

Melinda is involved in a year-long art project set for her class by Mr. Freeman. As part of that project, she's required to paint a tree. Over time, the painting of the tree comes to symbolize Melinda's emotional growth and the radical change she experiences in her self-perception. When she begins the project, it's notable that Melinda's watercolor reflects the negative way she perceives herself. She paints the trees as almost dead, completely surrounded by darkness. In her fraught emotional state, that's precisely how Melinda feels.
Later on, however, Melinda has a different conception of what she wants the tree—and by extension, herself—to be like. She hopes that the finished painting will depict a strong, sturdy oak tree reaching its branches upward to the sun, just as Melinda hopes to be strong enough one day to reach out to the people around her. When she finally completes the project, Melinda is pleased with her painting, just as she is pleased with the way her life seems to be turning out.