Neither (The Noctalis Chronicles, Book Three)

For Ava-Claire Sullivan, it's bad enough that loving vampire Peter Mackintire might kill him the rest of the way. His equally immortal mother keeps trying to murder her so Di won't lose another of her precious sons.
A promise Peter made nearly a hundred years ago means loving someone will kill him. Ava's done her best to either end her own feelings or stifle his, but she's losing; he's falling harder for her every night. She hasn't found a way to free him of his promise yet, and it's almost too late.
But her own terminally ill mother is dying fast, and now Ava-Claire is forced to choose between the last days of her mother's life and freeing Peter as they wait for Di to come up with yet another plan to destroy their love, and Ava's life.