Brzezińska was born in Opole and currently lives in Warsaw. She graduated in history at the Catholic University of Lublin and defended her PhD thesis in medieval history at the Central European University in Budapest. Her literary debut was her short story "A kochał ją, że strach", published in 1998 in the Magia i Miecz magazine, for which she received the Janusz A. Zajdel Award. Later she won the Zajdel Award also for the novel Żmijowa harfa and the short story Wody głębokie jak niebo. Brzezińska is a co-owner of the RUNA publishing house. In the Internet she uses the nickname Sigrid.