If you want my opinion, I don’t believe that’s a sin. Dante Alighieri himself had to rearrange Hell to fit his poetic needs. His favorite poets (Virgil is one of them) belonged to a time long before Christianity came to Europe. According to Medieval Catholicism, those that didn’t belong to the Christian Church were…well, to put it simply, damned. Dante rearranged Hell so that poets and men like Virgil would be placed in the First Ring of Hell: Limbo. Again, this is a place were those who haven’t belonged to the Church would be saved. The Inferno, as you might be referring to, is for poetic use. It doesn’t depict a theological explanation for were the unrepentant sinners and the damned go, but rather a beautiful depiction of allegory use in poetry. So again, I would say No, your use of Mary as a guide is not sinful