I like to think that the ghosts of Yáo Li Jie and Olesya Ilyukhina stayed with Grace through his time in the Hail Mary.
They were invested in the mision and dying even before they could fulfill their roles for the Project Hail Mary must be reason enough for them to have uncomplete things to do.
I like to think that they were accompaning Grace through his mission, giving him strenght to not lose his mind. That those moments in which he learned something about himself out of nowhere, or those sparks that lead them to solutions related to how to navigate Hail Mary were motivated by the efforts of Yáo and Ilyukhina to guide and help him.
Yáo and Ilyukhina not understanding they are dead at the start and thinking that they just wake up earlier (Yáo die first so he realize first in thinking this, when Ilyukhina dies Yáo explains to her that she did not survive the induced coma).
Yáo and Ilyukhina knowing that is cruel to wish for Grace to wake up sound and safe, just for him to be complete alone, but he is the only hope they have left.
Yáo and Ilyukhina feeling more at ease after Grace gives their corpses to the stars.
Ilyukhina been the most excited one about Rocky apparition, because she was an engineer and is just fascinated by what Rocky can do.
Yáo and Ilyukhina been indignated to have lost their chance to be part of the first contact in life.
Yáo trying to pass his knowledge as a captain to Grace, to ease his way with the controls.
Ilyukina been that little voice in Grace head of giving a chance to the Blip- A, that maybe they are friendly.
Yáo been a quiet force that supports Grace. There is point, at least in the book in which Grace seems to think that maybe he was brave, but he doesn't remember it, maybe that thought came from Yáo who believed that anyone could be brave.
All those little moments of luck been Ilyukhina and Yáo trying to influence so Rocky and Grace can have a successful mission.
Both ghosts, but specially Yáo bringing bad energies the moment they realize that Grace was sent against his will.
Ilyukhina crossing to the other side in peace the moment that realize that Rocky is the new engineer and that Grace has made the taumeba been able to survive Venus and the eridiani-2 planet.
Yáo crossing to the other side in peace when Grace decides to go rescue Rocky, because he can finally see Grace been truly brave for someone he cares.
If Grace has 2 ghosts taking care of him, Rocky has 22.
22 eridian ghosts noticing the Hail Mary first and making it more noticiable for Rocky (maybe they made subtle sounds or vibrations so Rocky would have a better picture of it).
The Blip-B and Blip-C having a perfect trajectory to the Hail Mary thanks to the 22 eridian ghosts.
22 eridian ghosts celebrating that their single survivor has been able to be part of the first contact.
The Hail Mary been the home of 22 eridian ghosts who come in all the sizes and shapes.
22 eridian ghosts been fascinated with the alien that Grace is and how leaky he is.
22 eridian ghosts concentrating their efforts so Rocky is able to recover after been burn by the oxygen.
22 eridian ghosts using their best clothes (they are ghosts they can wear whatever they want) as a celebration for having succed in doing the taumeba.
22 eridian ghosts not knowing what to do once Blip-A starts failing and Rocky is left without astrophage.
22 eridian ghosts crossing to the other side in peace once they hear the knock outside the Blip-A, because Grace is here.
Both ghosts, human and eridian, been able to "see", understand and "touch" each other and doing and alliance for sake of their two single survivors, who needed a team and a miracle, and all they got are ghosts and each other.
