The fact that the channeler went into the White Tower and was in a familiar disguise of black and white light is typical of Mesaana. Her weak punishment of Sheriam with a rubbish slap of Air is also reminiscent of her struggle to punish people on a level with the other Forsaken - they generally tolerate defiance very badly and the darkfriend ends up in agony.

However, Cyndane also has exceptional strength in the Power, and the disguise is described in some ways related to moons and stars. In the Prologue we also hear that she is going around sorting things out for the Last Battle, so she has her fingers in many pies, or wherever Moridin wants them. She could quite easily be in the White Tower, Black Tower, or anywhere - visiting many places every day.

The fact that the Forsaken wants Egwene to be deposed is either Mesaana changing her plans, or Cyndane countermanding them. Lanfear was notorious for meddling.