This pilot study employed an exploratory single-case design to examine the potential of generative AI in art therapy through a four-session program structured around the Expressive Therapies Continuum (ETC) and an AI role spectrum. The program was conducted with an art therapist experiencing role identity conflict, and session records, interview data, and artworks were collected and analyzed qualitatively. The results identified four therapeutic factors: emotional awareness and externalization supported by AI, enhancement of positive affect and perspective shifting through AI-generated images, identity exploration and integration through interaction with AI, and the role of image-mediated interaction and therapeutic relationship. The findings suggest that AI can function as a therapeutic medium in art therapy, facilitating emotional awareness, positive affect enhancement, and identity exploration. Furthermore, the therapeutic impact of AI-based approaches appears to depend more on therapist clinical judgment and contextual media selection than on the technology itself. This study provides preliminary data for future practice and research in AI art therapy.