Awful story. She probably had viral cardiomyopathy.
It is the flu that goes wickedly rampant and attacks the heart.
Usually the only treatment is transplant.
I'm sorry for your loss.
The evening before she died she asked the nurse "Am I going to die tonight" the nurse responded "not on my watch". The nurse finished her shift at 11pm and Loni passed away at 5:30am.
I think my niece new.