I believe Abigail was a representation of a the possibility of a "normal" life for Will and Hannibal, together.
Like, i agree with some people in the thought that they had more of a connection with what she represented, than who she was. The thought of them being together.
Don't get me wrong i do feel like they had a connection with her (Hannibal cause she reminds him of Misha, and Will cause she brings his paternal side). But she was nothing more than a gift, in Hannibal's eyes. Something to give to Will, if he followed him to this life, or to take away if he felt betrayed.
So her death is even more meaningful if you think that it's basically Hannibal saying "If you can't have this life with me, then you can't have this life with anyone else". She dies, and their normal life dies with, like the stag did.
Will tried to keep her alive, cause he wanted that life. But he had been too late to that realization, the realization that he picked Hannibal. And Hannibal took that as him picking Jack
Will hallucinating Abigail was more of him trying to understand why he wanted to go after a man that had done so much harm to him, and to others. He found it hard to accept the fact he wanted to be/ become a terrible man.
Also,, I don't think she would survive a family life with them, she would die in Will's or maybe in Hannibal's hands (possibly as a show how devoted they are to each other, willing to kill).
Because no person can survive their relationship if not themselves.
So yeah, in all probabilities, Abigail (Father's joy), was destined to die in her father's arms, it was just a matter of which one.
