Unbreakable

Victoria is Katherine's best friend, sire and they consider each other sisters. In 1498 Katherine had come across Victoria dying on the streets, just years after Katherine had turned.
Katherine saved Victoria by turning her into a vampire, and they ran from Klaus for over 500 years together. Whilst they ran, Victoria had a weird feeling about Klaus, like he had something of hers. She never told anyone, as it seemed irrelevant.
She then discovers that that feeling is very relevant and she finally meets her soul mate, Kol.