Nitocris is not mentioned in any contemporary sources -- no buildings, no mentions in biographies, no inscriptions -- but she is mentioned in the king lists of Turin, and by Herodotus and Manetho. Since we rely on these sources heavily, it seems reasonable to assume that she did indeed exist, but her role is in question.

The Turin canon lists her after Pepi II and (possibly) Merenre II and some other unknown pharaoh. The confusion is a reflection of the disintegration of the Old Kingdom, which led to theFirst Intermediate Period. She may be somehow linked to another king, Neterkare, who may have existed at the same time.

But Manetho is a bit suspect, as he asserts that Nitocris build the "third pyramid" at Giza (the one we attribute to Menkaure/Mycerinos). It's possible that he confused the name of Men-kaw-re with Nitocris' praenomen, Men-ka-re.

It is believed that she came into power when her brother (and possibly husband) Merenre II was murdered. The story is that she invited his murders to a banquet and then flooded the sealed banquet room with the Nile. Then, to avoid the wrath of the other conspirators, she committed suicide (apparently by running into a room of burning embers and flinging herself into the flames) A romanticized story, to say the least, but it has been retold for centuries.