In pirates of the caribbean 4, the fountain of youth exchanges the life span of 2 people soooo....?

how was angellica saved if blackbeards lifespan was going to be about the same as theres in the first place since they both touched the sword that was poisoned by barbossa. blackbeards lifespan was transferred to angellica but that means that she would have only gotten a few minutes more of life correct. i thought this was a great movie but i dont understand this part