Based on your daughter's interests, personality, and aspirations, I would recommend:

Georgetown Day School (GDS) - DC
GDS is known for its progressive education philosophy and strong arts programs. The school cultivates a collaborative and inclusive learning environment that encourages students to express their creativity and individuality. GDS has a robust visual arts curriculum, with courses in drawing, painting, ceramics, photography, and more. The school also emphasizes interdisciplinary learning, allowing students to explore connections between art and other subjects like writing and humanities.

Moreover, GDS has a strong creative writing program. Students can take courses in poetry, fiction, playwriting, and journalism, among others. The school also publishes student-led literary magazines and hosts writing competitions and workshops.

The nurturing and supportive community at GDS would likely be a good fit for your daughter's kind and collaborative nature. The school values diversity, equity, and inclusion, fostering a welcoming environment for all students.

Holton-Arms School - MD
Holton-Arms is an all-girls school that provides a well-rounded education with a focus on empowering young women. The school has a strong visual arts program, with courses in drawing, painting, sculpture, digital media, and more. Students can showcase their work in the school's art gallery and participate in art clubs and competitions.

The school also offers creative writing courses and extracurricular opportunities, such as a literary magazine and writing contests. Holton-Arms emphasizes the importance of finding one's voice and developing self-confidence through writing.

As an all-girls school, Holton-Arms provides a supportive and collaborative environment that encourages girls to take risks, express themselves, and develop leadership skills. The absence of gender stereotypes and competition with boys may be particularly beneficial for your daughter, given her kind and non-competitive nature.

While National Cathedral School is also an excellent school, its more traditional and rigorous academic approach may not be the best fit for your daughter's artistic interests and collaborative personality.

Ultimately, I recommend visiting both GDS and Holton-Arms, if possible, to get a better sense of the school culture and community. Talk to current students, teachers, and parents to gather more information. Trust your instincts and choose the school that feels like the best fit for your daughter's unique needs and aspirations.