It's not physical absorbtion. It's soul absorbtion.
Now there was a change in the way the patient librarians were working, she saw. Some were making a space in one block of shelves, and others were bringing in a new stack of material, its details too remote to make out. She knew what they were doing. That was her own pitiful heap of memories, her whole life of a mere few decades dwarfed by the great banks of knowledge here. And yet she would be given a place here; she would be cherished. Others would be able to access her memories as easily as she could, just as she could reach the memories of others—and even the greater collective experiences of the Transcendence itself, which she perceived now as shadowy mountains of information looming beyond the bounds of the archive.
And, constantly remembered, the memories that defined her need not die with her—and so she need not die, not ever. She had no need of Reath's "immortality pill"; in this chill, remembered sense, she was already an undying.
She rose again, lifting up through some impossible dimension, so that the whole of the Transcendence opened up around her. Now in her metaphoric perception it was as if she was in a starship, in a hold so vast she could barely make out its walls. Huge, dimly seen masses drifted through the receding gloom. But even this space was not the full extent of the ship, for corridors and walkways led away, receding in every direction, all around her, leading to hollow, silent spaces she could never reach, not if she explored for many lifetimes. This was the mind of the Transcendence. But all she saw was merely a fraction of the vastly complex infrastructure of this place, this mind.
Even now she was still outside the Transcendence, in a sense. She was still herself, still small and closed-over and complete. But there was a place for her here in this immense cathedral of mind. All she had to do was take one last step.
She had a final moment of doubt. It was as if she looked back at herself, her body lying peacefully now on its pallet.
And then she let the embrace of the Transcendence enfold her at last.