I unfortunately do believe that Nanamo is dead, but... There definitely is one way in specific that she could still be alive.
The drug Somnus.
Somnus is well-known in the back alleys of Ul'dah. When it is taken in over-abundance, the user falls into perpetual sleep, not unlike some kind of Sleeping Beauty. Considering the enemies' reluctance to show the corpse, it could be because she's sleeping. Teledji Adeledji may undoubtedly have wanted her dead, but Lolorito may have planned ahead and tried to switch things with Somnus to play into his own hands better.
All of this said, the scene where Nanamo succumbs to the poisoning was brutal and is why I am not sure I believe she is simply overdosing on Somnus.