Nothing she tried could bring Jeremiah back to her. He may have healed as best as what was expected from being burned in Ace Chemicals. He may have fooled them all for a while, but when he was informed Bruce was dead it became real. There was no long con, no willingness, his obsession and grief proving the better prison than the asylum he was inside.  No punch line, just grief, obsession and emptiness. 

The Proxy tried so many things as she pretended as a nurse, as she carried out the cover and  desperately tried to keep followers, keep fear and people to work for them. It started off little by little, his legend lost by the new thing haunting Gotham from outside the walls. People saying his name like he was dead already.  She dreamed of him suddenly snapping out of it, she would wait for his reaction.

Finally Ecco brought him out of the asylum, she dug into the grave and left him with Bruce's body. Hoping for a reaction. Feeling that he deserved more, that she needed to see him rise again...  He just stayed there, as she listened for his breathing and fired twice. Once in his head, and once her in her own. 

Bruce won without lifting a finger. The officers were understandably disgusted when they reported to the scene but Gotham was relieved, saved of a burden, a legacy forever. The devotion, the life she threw away might have been nothing more than a joke.