She has also published two heroic fantasy series, The Witches of Eileanan[2] and Rhiannon's Ride, the poetry collection Radiance, and the novel Full Fathom Five under her maiden name, Kate Humphrey.

Writing in The Sydney Morning Herald Melanie Kembrey rates Forsyth as an "internationally acclaimed author...best known for her re-imaginings of fairy stories from a feminist perspective.

"[5][6] Forsyth wrote "Full Fathom Five" as the thesis for her Master of Arts in Writing, and then, to relieve the tedium of studying theorists such as Lacan, Derrida and de Saussure for her exams, she started reading a multi-book fantasy series.

[14] Forsyth is active in presenting workshops for writers,[15][16] and is a frequently a public speaker,[17] often in schools,[18] and also in literary festivals and conferences,[19] bookshops, libraries and museums,[20][21] on fantasy, folk tales and the role of women in them.

[23][24] Forsyth is a generous mentor for, and collaborator with, other writers and creatives including co-author Kim Wilkins and illustrator Kathleen Jennings for The Silver Well, which won the 2017 Aurealis Award for Best Collection; Sarah Mills with whom she presented the combination cooking and book-review show Word of Mouth TV; artist Lorena Carrington[25][26] with whom she partnered on Vasilisa the Wise and Other Tales of Brave Young Women in 2019 and others in their series of illustrated feminist fairy tales since;[5][27] and with sister Belinda Murrell for joint research on their Searching for Charlotte.