At some point prior to 1899, Dutch killed the brother of his one-time associate Colm O'Driscoll, who in return took Annabelle's life. Her death would start a long-standing feud between the Van der Linde gang and the O'Driscoll Boys.
Events of Red Dead Redemption 2
Annabelle was mentioned several times by Dutch, Hosea Matthews and Arthur Morgan in conversations between the three. She is later mentioned during a confrontation between Dutch and Colm; whereas Colm claims he didn't particularly like his brother, Dutch firmly replies that he did like Annabelle.
Her death would be eventually avenged after Colm was arrested by the government to be hanged and any attempts to save him by his gang were dashed by Dutch, Arthur, and Sadie Adler.