In Nepal, a Kumari is a prepubescent girl selected from the Shakya caste or BajrSacharya clan of the Nepalese Newari Buddhist community. The Kumari is revered and worshiped by some of the country’s Hindus. While there are several Kumaris throughout Nepal, with some cities having several, the best known is the Royal Kumari of Kathmandu, and she lives in the Kumari Ghar, a palace in the center of the city. The selection process for her is especially rigorous. As of 2017, the Royal Kumari is Trishna Shakya, aged three, installed in September 2017 by the Maoist government that replaced the monarchy. Unika Bajracharya, selected in April 2014 as the Kumari of Patan, is the second most important living goddess.
The worship of the goddess in a young girl represents the worship of divine consciousness spread all over the creation. As the supreme goddess is thought to have manifested this entire cosmos out of her womb, she exists equally in animate as well as inanimate objects. While worship of an idol represents the worship and recognition of supreme through inanimate materials, worship of a human represents veneration and recognition of the same supreme in conscious beings.
In the Shakta text Devi Mahatmyam, or Chandi, the goddess is said to have declared that she resides in all female living beings in this universe. The entire ritual of Kumari is based on this verse. But while worshipping a goddess, only a young girl is chosen over a mature woman because of their inherent purity and chastity.
As said by Sabinaya Pantha