THR is reporting that Taryn Manning (8 MILE, SONS OF ANARCHY) will be a regular for the upcoming CBS remake of Hawaii Five-O.
She will be playing Mary Ann McGarrett, sister of Lt. Commander Steve McGarrett (Alex O’Loughlin).
Mary Ann is a totally new character and was not in the original series. The casting call sheet describes her as:

McGarrett’s younger sister, she’s a punked-out young woman with a checkered past, including stints in rehab and several brushes with the law. Mary has been acting out ever since her mother’s early death, at which point she felt effectively abandoned by her father — an apparent betrayal she’s still trying to work through. When she shows up high at their father’s funeral, McGarrett is enraged — but under his anger, he has a deep and loving bond with his sister, although that has been stretched to the breaking point in recent years. However, Mary’s realization that her father’s apparent neglect may have actually been his attempt to protect her from a mysterious menace just may inspire Mary to turn her chaotic life around

Manning is the third actor announced for the series, joining Alex O’Loughlin (McGarrett) and Daniel Dae Kim (Detective Chin Ho Kelly).