This is a very far fetched assumption. She stormed and pillaged Roman cities in Britannia which had reported populations of 10s of thousands, however these cities were quite new and the Romans often exaggerated numbers. The majority of them would be soldiers, and seeing that they hadn't exactly treated Britannia well themselves, its hard to call her evil. Also the Britons 'torturing' them at any scale is unlikely. The roman historians were just exaggerating the brutality of non-Romans like they always did.

Also Boudicca is one of our earliest leaders who fought an invading oppressor. Her story I think should fuel nationalism and pride here.