Boudicea was a Celtic Queen of the Icenni tribe in ancient England. She had two daughters--what position she assumed when she conceived them is anyone's guess, but eventually she led a revolt against the Romans who were occupying the country at that time.
She won a few victories and people flocked to her. Soon she came toward London with a huge army. Knowing they could not defend the city, the Romans abandoned it, leaving the Romanized Brits at her mercy.
And she was not very merciful. She burned the city to the ground and tortured and crucified hundreds of people. The Romans eventually took a stand against her. They had a small army, and Boudicea's forces were so confident of victory they brought their families along and brought wagons to carry off the plunder they planned to strip from the dead Roman soldiers.
Mistake. Though the Roman Army was smaller, it held an advantageous position on the field and was better armed and better disciplined. They defeated Boudicea's forces--in fact routed them. They fled the battlefield only to become entagled and blocked in the wagons they had brought. The Romans killed almost all of them and captured their wives and children for sale as slaves.
Boudicea escaped. She killed her two daughters and herself to avoid being captured and paraded through the streets of Rome and then executed.
Sad story. To some people, she is heroic. She stood courageously against oppressors and gave them a good fight even if she lost in the end. Others, however, point to her brutality when she destroyed London. So she gets mixed reviews.
If Lewis used her as a model for the White Witch he is certainly only showcasing her bad side.
David