Forrester was born in Lower Hutt, Wellington to parents Amos (Ngāti Porou) and Robyn, who is Pākehā.

She attended high school at Wellington Girls' College, where she was involved in drama productions and the kapa haka roopu.

Among her inspirations, Forrester cites Rachel House, Nancy Brunning, Miriama McDowell, Madeleine Sami, Billy T. James, Kristen Wiig, Tina Fey, Hannah Gadsby, Jackie van Beek and her family – particularly on her Māori side in Tokomaru Bay, a small community near Gisborne on New Zealand's East Coast.

On television, Forrester has had leading roles in Auckland Daze, Super City, Find Me A Māori Bride, The Barefoot Bandits, The Adventures of Suzy Boon, Jandal Burn, Golden Boy and Educators.

[3] Theatre credits include Perplex, Camping, Ngā Pou Wahine, The Wholehearted, Amadeus and When Sun and Moon Collide.