[2] Harper began her career in art museums in 1983 as assistant curator in the International Prints and Illustrated Books department of the National Gallery of Australia.

[5] In 1988 and 1989, Harper was part of the Institutional Planning Team for the Museum of New Zealand Te Papa Tongarewa, and from 1990 the director of the National Art Gallery, Wellington, until legislative change took effect in 1992 at which point she became the Director, Art and History, Museum of New Zealand Te Papa Tongarewa.

[11][12] During the closure Harper led the crowdfunding drive to raise funds for the acquisition of Chapmn's Homer a sculpture by Michael Parekowhai, [13] part of the artist's installation at the 2011 Venice Biennale.

[16] Her tenure is noted for her fundraising efforts, in addition to increasing visitor numbers and expanding the gallery's permanent collection to have a stronger national and international remit.

[17] Harper was the Commissioner for New Zealand's representations at the 2009, 2011 and 2013 Venice Biennales (featuring Judy Millar and Francis Upritchard, Michael Parekowhai, and Bill Culbert respectively).