Each main female pirate of the last eras has conquerors Haki; Big Mom and Hancock. It only makes sense that the main female pirate of this era has it as well.
Oda has also hinted at it in a gag in Wano where he juxtaposed the scene of Luffy knocking out everyone in the prison with Nami knocking out the bathhouse with her happiness punch in the same chapter.
Oda has also hinted at it in a gag in Wano where he juxtaposed the scene of Luffy knocking out everyone in the prison with Nami knocking out the bathhouse with her happiness punch in the same chapter.