The dev provided the option not to kill which was the main problem people had if I remember correctly. He did an excellent job in the early stages of the story, which is obvious with the large part of his audience who loves her character. I went out and bought the model. She is such a damn cute little model and the dev made her in to a much loved character.I think is a consensus people did not liked that vampire thing, so much so that dev came with that purification thing after.
On the other hand, MC being half angel means he is immortal, so would be really sad for him seeing Eliza getting older until she dies, remember the Highlander movie.
From a plot POV, Vampirism was an easy option. There are other options the dev could have chosen, but didn't, which is his prerogative as the dev of course. I'd have taken another option. Turning someone so sweet in to a murderous vampire was not the best plot choice IMO.
I agree it is tragic to think of her dying while the MC lives on. I'd rather that than the vampire option. I can understand his desire to make her long lived and someone of power to aid the powerful MC he has created. Still, its a great story so far. One major hiccup is pretty good. I'm looking forward to the rest.