Who ordered Melindhra and why?

Nynaeve and Birgitte were eavesdropping on the Forsaken Conference in Tel'aran'rhiod. Rahvin says, "He [Rand] will concentrate on you [Sammael], ... If need be, one close to him will die, plainly at your order. He will come for you. And while he is fixed on you alone, the three of us, linked, will take him. What has changed to alter any of that?" (TFoH: 34, 550, A Silver Arrow, 390)

(TFoH: 51, 871, News Comes To Caemlyn, 617):
So, it seems Melindhra was ordered to kill Mat with a golden bee dagger if the need arose. Mat let slipped to her that Rand's going to Caemlyn, instead of "concentrating of Sammael", and she attacked Mat right away.

This FAQ compiled by Pam Korda (kor2@midway.uchicago.edu) and converted to HTML by Matthew Hunter (mhunter+@andrew.cmu.edu).