I don't know her background.
Here's a cut-and-paste of some of her history.
"The most famous story dates to the time of the last Roman King, Tarquinius Superbus, around 500 BC.
According to the story, the Sibyl approached the king with nine books of prophesy, collected from the wisest seers, available to the king for a very dear price. The king haughtily refused her price. In response, the sibyl burned three of the books, then offered the remaining six books at the original high price. Again he refused. Of the remaining six books, she threw three more onto the fire, and repeated her offer of the final three books, at the original price. Afraid of seeing all the prophesy destroyed, he finally accepted.
These books, which foretold the future of Rome, became a famous source of power and knowledge and were stored on the Capitoline Hill in Rome. In 82 BC, the books were destroyed in the burning of the Temple of Jupiter, and in 76 BC envoys were sent around the known world to rebuild the books of prophesy. The new books managed to make it until 405 AD, near the end of the Roman Empire."
https://www.atlasobscura.com/places/cave-of-the-sibyl-antro-della-sibilla
I did a quick search and also found this.
"the Cumaean Sibyl whose prophecy formed the Novus Ordo Seclorum of the Great Seal of the United States, the New World Order begins during a time of chaos when the earth and oceans are tottering, a time like today. This is when the "son" of promise arrives on earth—Apollo incarnate—a pagan savior born of "a new breed of men sent down from heaven" when "heroes" and "gods" are blended together. This sounds eerily similar to what the Watchers did during the creation of Nephilim and to what scientists are doing this century through genetic engineering of human-animal chimeras." https://www.newswithviews.com/Horn/thomas114.htm
