I’m inclined to believe it simply for the fact that the candle worked. The name of the person had to be said over their heart and then the heart had to be inside the body (if it wasn’t already). The fact that Snow said the name “Cora” over the heart and that when a heart was put back inside Cora it instantly healed Rumple I would have to believe that it was in fact her heart and that she is now dead.
I can see where you’re coming from but the last time Cora was “dead” she simply didn’t have her heart inside her so it was easy for her to trick Regina with Hook’s help.
I really do think she’s gone this time and had a nice moment with her daughter and Rumple in the end. The fact that she did seem to have that moment of clarity also seems to point to it definitely being her heart, simply because anybody else that has been brought back with the wrong heart hasn’t come back to their normal selves. Aurora & Cora seem to be themselves whereas Daniel came back “wrong.”
Keeper of Hook's Trenchcoat.