Rites of First Blood by Karen Dale Wolman

Sara Hansen, a New York lesbian doctor travels to the Amazon jungle to research a plant that boosts the immune system against AIDS. While hiking up a tributary of the Amazon River one morning, she gets involved in a hunting accident with the Onasaki. Living deep in the jungle, this is the matriarchal hunting and gathering tribe's first contact with Western civilization. Lost from her colleagues, Sara goes back with the tribe and becomes lovers with Olani, the shaman and healer to the Onasaki. While a search party gets closer and Olani battles with the poweful daughter of the tribal chief, Sara must decide between two lives.