Just a reminder
-Tataru random depression since ~2.3 wanting to get stronger/find a purpose
-Nanamo finding herself powerless since 2.3-2.4
-Tataru actions on 2.55
-Random Tataru dialogue saying she wanted to find a final ingredient to finish a tonic
-Tataru always moving around
-Nanamo and Tataru were never seen together even during the banquet (Tataru was on mordhona markets)
-Nanamo likes to sneak out of her castle (lady lilira)
-Urianger gave Tataru a disguise spell in case imperials attacked again
-Escape tunnel is inside Nanamo room (where she died) and yet no reaction from the scions. While Teledji just arrested the player and went to the banquet, doubt he'd bother to discard the body during a coup.
-Teledji/Lolorito objective is to seize Carteneau flats and excavate omega weapon, that's why they wanted to topple the monarchy and yet lolorito is displeased for something (doubt is due the warrior of light escaping since the servant says "everything went as planned").
While only theorycrafting, nanamo is most likely still alive. Either with tataru working with nanamo or tataru being nanamo in disguise, it's not like it would be hard to pull off since both scion HQs were in thanalan area (mor dhona is really just outside n thana aether and the disguise spell would make sneaking past the imperial base easy). Though, it might just be storyline plot holes.