So far, no reason has been given for her death.
With no experience courting a potential bride - his sexual experiences confined to slaves and whores - Hammond ultimately chooses his cousin Blanche for his wife in what would not be considered a courtship in its true sense.
Concurrently, Hammond also purchases Mede, a Mandingo, as a slave, something Warren had always wanted because of their physical strength.
Blanche, in return, takes her anger out on Hammond in the only way she knows how.
Maybe it's no accident that that feels liberating.