Gayatri Jayanti: the greatest Fire Sacrifice
Some sacrifices require a being be unmarried, others require a being be married. Of those which require marriage, some require both the feminine and masculine, others do not. When Brahma first attempted the Fire Sacrifice, he could not complete it because Brahma was not masculine, and "he" was not married to the feminine. He desperately sought the very first being he might find to be his wife, and Gayatri - whose structure of words is used in the Fire Sacrifice - so greatly desired the completion of the sacrifice that Gayatri manifested Shakti, and took the feminine form. She embodied herself to be nearest to Brahma. The two at that moment developed a pure love, and were married. This mutual desire to complete the sacrifice for the sacrifice's sake, which is expressed in the purest love of Brahma and Gayatri, also expresses the essence of Kama, which Kamadeva espoused. This was the moment the most sacred fire was kindled.
Gayatri Jayanti is celebrated by repeating this fire sacrifice with one's spouse, and kindling that love which burns with the brightest and warmest of flames. The fire kindled by love between spouses is the brightest and hottest fire, required for Sacrifice, kindled by self-control.
She is typically portrayed as the maternal form of her several Avatars: Gayatri, Laxmi-Saraswati, Sati-Gauri, etc. because she is the supreme Adi-Shakti, the wife/half of Brahma, Vishnu, Shiva, and all other non-beings, and the act of motherhood is the fulfillment of this form. But she is also portrayed in the moment before she met Brahma, using a mirror for beautifying herself to make herself attractive to him: just as we may all, using the reflection improve ourselves toward an ideal. She is also sometimes portrayed as Mother Gayatri, holding all the weapons and tools of the many beings of the universe: as Shakti, she can take all form. She is the process of education, whether the learning that all mothers bestow upon their progeny of survival, or the subtle learning of the Vedas.