Final answer:
The specific mythological figure related to Plains Indian women and quillwork isn't addressed in the information provided, but quillwork is a historic Native American art form perfected by these women, showing their cultural significance.
Step-by-step explanation:
The mythological figure believed to have given the art of quillwork to Plains Indian women does not appear explicitly in the information provided. However, discussing Native American art and artists, quillwork is a unique art form to North American Natives historically used for decoration, utilizing porcupine quills before the introduction of European glass beads. Plains Indian women were adept at quillwork, often using dyed quills to create intricate designs on various materials, such as leather and cloth. The skill and artistry of quillwork are reflective of the rich cultural traditions of the Native Americans, much like the work of Ellen Neel, Nora Naranjo-Morse, and the significance placed on women in their societies.