During Chapter 41 of A Feast for Crows, Littlefinger discusses Cersei's incompetence as a ruler in King's Landing, and says:
What little peace and order the five kings left us will not long survive the three queens, I fear.
Given that Littlefinger has never openly acknowledged Daenerys as a player in the Game of Thrones, who are the three queens that Littlefinger is referring to?