Armstrong published two children's books in the early 1980s, Enwhisteetkwa (or Walk in Water) in 1982 and Neekna and Chemai the following year.
She did research for two years in preparation for writing Slash (1985), her first and most famous novel (Petrone 179 and Lutz 22). Armstrong's novel was commissioned by the curriculum project, for use as part of a grade eleven study in contemporary history. Armstrong wanted Slash to connect with and relate to contemporary students (Jones 60). She took on the project to forestall the work of more famous non-Aboriginal authors, who were "dripping at the mouth" to document Native history (Williamson qtd in Jones 60).
Slash explores the history of the North American Indian protest movement through the critical perspective of central character Tommy Kelasket, who is eventually renamed Slash. Tommy has encountered intolerance in an assimilationist school system and racist North American society, but his family encourages him to be proud of his Okanagan heritage. He becomes an activist for Aboriginal rights. Armstrong has said that Slash is not a chronicle of AIM (American Indian Movement); rather, the text provides a personalized account of the origins and growth of Native activism since the 1960s (Lutz 22 and Jones 51).
Since Slash was published, Armstrong has written in a variety of genres and is widely published. Her poetry is collected in anthologies and her collection Breath Tracks (1991). Her short stories are collected in works such as All My Relations: An Anthology of Contemporary Canadian Native Fiction, edited by Thomas King. Armstrong's second novel, Whispering in Shadows (2000) traces the life experiences of a young Okanagan activist woman.
In addition, Armstrong has published critical works, such as The Native Creative Process. This is a collaborative discourse between Armstrong and Douglas Cardinal on Aboriginal artistry. In Land Speaking, she addresses how land and the Okanagan language influence her writing.
