Victoria is seeking revenge against Bella after the loss of her lover. She never expected Bella to welcome her presence, asking for help in seeking revenge against Edward for breaking Bella's heart.
Everyone knew of her, of her doings, knew of her supposed power yet no one believed , for them it was all a myth, another gruesome story, a legend... a prophecy. And she was there, to prove them all wrong when they were expecting it the least at that too.