A Chance
Back when Anastasia offered to help revive Elorin's parents, it was because she, too, knew the kind of danger he would be. Even with her simple thought processes, she thought that it would be easier to control Elorin in the future if he was very grateful to Leonel.
It was a good idea, but the simple-minded little World Spirit had never connected the fact that this might help Aina's parents as well. At the very least, if she had brought up the idea earlier, it would have been possible. But she only brought up the idea right after Aina had just become a Seventh Dimensional existence.
According to Anastasia, the problem with Aina's Dimension being too high was that now the link to her mother was being weighed down.
With the Silver Tablet, back then, Leonel could revive up to the Seventh Dimension. With Anastasia's ability to reverse the flow and peek into the stream of time itself, it would work.