The following press release confirms Summer’s role & which episode she’ll be appearing in; 3×16 ‘Kekoa’ which is due to air next Monday, February 11 on CBS — her character’s name is Maggie Hoapili. Hopefully we’ll see some promotional images soon!
“Kekoa†(Hawaiian for “Warriorâ€) – Five-0 investigates the murder of a Lua (ancient Hawaiian hand-to-hand combat) master, and McGarrett hires a private investigator to follow his mother, on HAWAII FIVE-0, Monday, Feb. 11 (10:00-11:00 PM, ET/PT) on the CBS Television Network. Christine Lahti returns as Doris McGarrett. Treat Williams guest stars as a private investigator hired by McGarrett to follow his mother, and Summer Glau guest stars as the daughter of the Lua master who comes to Five-0 for help.
Source:
http://summerglauweb.org/hawaii-five-o-press-release/