Who is Victoria from Eclipse and what is their importance?

Victoria is a vampire who first appeared in the original book in this series, Twilight. Victoria, her lover James, and another vampire called Laurent came to Forks and had a confrontation with the Cullens. Later there was a battle between the two families and James was killed. To get revenge, Victoria has vowed to kill Bella because Edward is responsible for James' death and Victoria feels that if she lost her lover, Edward should lose his.