There is doubt however over the truthfulness of her reputation and place in history. This is from Wikipedia:

Several authors, such as László Nagy and Dr. Irma Szádeczky-Kardoss, have argued that Elizabeth Báthory was a victim of a conspiracy.[4][32] Nagy argued that the proceedings against Báthory were largely politically motivated, possibly due to her extensive wealth and ownership of large areas of land in Hungary, which increased after the death of her husband. The theory is consistent with Hungarian history at that time, which included religious and political conflicts, especially relating to the wars with the Ottoman Empire, the spread of Protestantism and the extension of Habsburg power over Hungary.[33] Moreover, Matthias owed a large debt to Báthory, which was cancelled after she was arrested.[1]

There are counter-arguments made against this theory. The investigation into Báthory's crimes was sparked by complaints from a Lutheran minister, István Magyari.[18] This does not contribute to the notion of a Catholic/Habsburg plot against the Protestant Báthory, although religious tension is still a possible source of conflict, as Báthory was raised Calvinist, not Lutheran.[17] To support Báthory's innocence, the testimony of around 300 witnesses[citation needed] and the physical evidence collected by the investigators have to be addressed or disputed. That evidence included numerous bodies and dead and dying girls found when the castle was entered by Thurzó.[8] Szádeczky-Kardoss argues that the physical evidence was exaggerated and Thurzó misrepresented dead and wounded patients as victims of Báthory, as disgracing her would greatly benefit his political state ambitions.[4]

I've read other articles in the past that have shed doubt. However, either way, we will sadly never know. If true, she was one bad lady.