I like to listen to the song. God is a girl.
So, I got curious.
Are there any Goddesses in any scriptures who are girls.
By girls I mean those that they look like around 13 years old.
Bālā Tripurasundarī or Kumārika is a form of Adi Shakti who is worshipped in the form of a girl who is around 9 years old.
She is worshipped by people during the first two days of Navaratri. Girls of age 8 are respected and regarded as the form of Bala Tripura Sundari. They are bought new clothes. It is believed that this Goddess can be easily pleased through worship.
She is mentioned in the 26th Chapter of the Lalita Mahtmya of Brahmanda Purana.
73-77a. She was the daughter of Lalita Devi. She always stayed near the goddess. She was worthy of being worshipped by all Shaktis. She was an adept in martial feats and exploits. Her form and features were like those of Lalita. She was always like a nine year old girl yet she was a great mine of all lores. Her body was like the rising sun. 11cr creeper-like slender body was in complexion. She was perpetually present near the foot-rest of the great queen. She was at it were the vital breath of the goddess moving externally. She was her fourth eye. She became curious and thought thus : “I shall immediately kill those sons of Bhanda who have come here’. After making up her mind thus. Balamba submitted to the great queen.
77b-80 Mother, the sons of Bhaņḑa, the great Daitya, have come to fight. I wish to fight with them. I am interested in this because I am a young girl. My arms throb with an itching sensation for war. This is my playful activity. It should not be curbed by your orders for prohibition. Indeed I am a girl loving toys and playful pastimes. By this play of fighting for a moment, I shall become delighted mentally.
Lalita Devi tries to prevent her from fighting because she is tender and a small girl.
81-83 Dear child, your limbs are very tender and soft. You are only nine years old. This is your first step and performance. Your training in warfare is fresh and recent. You are my only daughter. Without you, my breathing activity does not go on even for a moment. You are my very vital breath. Do not go in for the great war. We have Daņḑinī, Mantriņī and crores of other great Śaktis for fighting. Dear child, why do you commit this blunder?
Despite this, she manages to convince her mother to allow her to fight, and she participates in the war with Bhandasura. Lalita Devi gives some of her armour and weapons to her. Both the armies of Shaktis and the daityas were surprised when she came to the battle field and fought vigorously in the battle.
Apart from Sarvabhouma's answer, there is one more living goddesses that i found in wiki.
Kumari, or Kumari Devi, or Living Goddess – Nepal is the tradition of worshipping young pre-pubescent girls as manifestations of the divine female energy or devi in Hindu religious traditions.In Nepal, a Kumari is a pre-pubescent girl selected from the Shakya caste or Bajracharya clan of the Nepalese Newari community. The Kumari is revered and worshipped by some of the country's Hindus. A Kumari is generally chosen for one day and worshipped accordingly on certain festivals like Navaratri or Durga Puja. In Kathmandu Valley, this is a particularly prevalent practice. A Kumari is believed to be the incarnation of Taleju. When her first menstruation begins, it is believed that the goddess vacates her body. Serious illness or a major loss of blood from an injury also causes for loss of deity.
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 inanimate as well as inanimate objects. While worshiping a goddess, only a young girl is chosen over a mature woman because of their inherent purity and chastity. In Nepal, Kumaris are worshiped only for a day; often a few hours. Usually one cannot be a Kumari beyond 16 years of age because of menarche. The main target of a Kumari puja is to realize the potential divinity in every human being, mostly female. A Hindu spiritual aspirant sees the universal consciousness of humanity.
Whilst the veneration of a living Kumari in Nepal is relatively recent, dating only from the 17th century, the tradition of Kumari-Puja, or virgin worship, has been around for much longer. There is evidence of virgin worship taking place in Nepal for more than 2,300 years. It appears to have taken hold in Nepal in the 6th century. There is written evidence describing the selection, ornamentation, and worship of the Kumari dating from the 13th century CE.
Once Taleju has left the sitting Kumari, there is a frenzy of activity to find her successor. Some have compared the selection process to the process used in nearby Tibet to find the reincarnations of Tulkus, such as the Dalai Lama or the Panchen Lama. The selection process is conducted by five senior Buddhist Bhajracharya priests, the Panch Buddha, the Bada Guruju or Chief Royal Priest, Achajau the priest of Taleju and the royal astrologer.Eligible girls are from the Newar Shakya caste of silver and goldsmiths. She must be in excellent health, never have shed blood or been afflicted by any diseases, be without blemish and must not have yet lost any teeth. Girls who pass these basic eligibility requirements are examined for the battis lakshanas, or thirty-two perfections of a goddess.
Some of these are poetically listed as such:
In addition to this, her hair and eyes should be very black, she should have dainty hands and feet, small and well-recessed sexual organs and a set of twenty teeth.
Once the Kumari is chosen, she must be purified so that she can be an unblemished vessel for Taleju. She is taken by the priests to undergo a number of secrets Tantric rituals to cleanse her body and spirit of her past experiences. Once these rituals are completed, Taleju enters her and she is presented as the new Kumari. She is dressed and made up as a Kumari and then leaves the Taleju temple and walks across the square on a white cloth to the Kumari Ghar that will be her home for the duration of her divinity.
Devi Kanya Kumari is goddess Shree Bhagavathy in the form of an adolescent girl child. Devi is also known as Shree Baala Bhadra or Shree Baala. She is popularly known as "sakthi" (Durga or Parvati) "Devi". The Bhagavathy Temple is located in Cape Kanya Kumari in Tamil Nadu.
For more information see https://en.wikipedia.org/wiki/Devi_Kanya_Kumari