Which sentence, if added after sentence 6, would best create a strong, descriptive image that helps to explain why Rachel feels comforted?

She was young yet carried herself with great confidence, and her clear eyes locked onto mine and oozed kindness.
Dr. Perez was the youngest-looking dentist I had ever seen. She looked to be only a few years older than me.
I knew that I would like Dr. Perez and would never again be so anxious before a dentist appointment.
Dr. Perez moved quickly around the room, quietly gathering her dental tools.