"suffering the most frightful torments"
A scene from Dante's Inferno, showing heretics in burning tombs, engraved by Gustave Doré
Public DomainA scene from Dante's Inferno, showing heretics in burning tombs, engraved by Gustave Doré

This is a rare anachronism on Graves's part. The fear that he attributes to Livia is not a fear that a First Century pagan Roman would have entertained. The Hell that she fears is that of Dante, not Virgil.