Poor choice of words on my part. You mentioned yourself that the monetarists need the monarchy to stay in power, but that the only reason they would withhold announcing Nanamo's death is because she's alive. Isn't that backwards? They need her, but TelAdel killed her, so now they need some new way to keep her as a figurehead for as long as they can. The ruse probably can't hold.
On the subject of the poisoning itself:
If it was Somnus, then she could very well be "alive" but in a comatose state. There is a huge problem with the credibility of this theory, and it boils down to a contradiction in the established facts. Somnus is described as a recreational drug, capable of inducing coma in sufficient quantities. While it could have been used, there problem lies with the depiction of the poisoning itself. A "natural causes" type poison, like arsenic, or the oft-embellished cantarella, could induce a death-like sleep, but those are slow-acting poisons. Whatever was used to poison Nanamo hit like Doomtrain going at full speed.
What they showed us on screen was a rather specific type of poisoning: sudden seizures, followed by loss of breath, ending with cardiac arrest. These are all symptoms of poisoning by cyanide (or, as George RR Martin calls it, to get around the glaring anachronism, "the Strangler"). Cyanide poisoning... is final. There are antidotes, but nothing that can save a patient from a dose large enough to cause the immediate onset of symptoms.
If she's not dead, then there's definite necromancy involved. This would not be unusual for Ul'dahan politics at this point. The only way I can see them revealing her to be "alive" without cheapening the emotions of 2.55's events is if Lolorito is keeping her as a trump card to destroy the credibility of anyone who tries to prove otherwise. If that is his plan, there is no way she'll be anything like she was before.
We may see her again, but I don't think they can pull a happy reunion scene for her after that.