[4][5] While at Canterbury she studied under noted Christchurch artists Cecil F. Kelly and Archibald Nicholl.
[6] She lived and worked overseas for 30 years in Australia, Cyprus, Uganda, Lebanon, Italy and France before returning to New Zealand in 1983.
[7] Grehan studied ceramics under Alfredo Galicamo, specialising in modelling mythical beasts and figures.
[4][5] Grehan took on the role of vice-president of the Whanganui Art Society, and was a mentor to young artists.
[4][8] Much of Grehan's art was about women, and often featured symbols linked to nature, wisdom and sensuality.