I think we need more media in which Grace isn't all that happy of Simon presence, getting to even dislike, or just avoid Simon.
We know that Grace is very kind and considerate with Rocky, but I think that their relationship is unique beyond the connection they share, because they found each other fascinating and they needed each other help, they needed to trust and put and effort to work as a team for the sake of their planters, and they both were longing for interaction since they have been isolated. I'm not saying that they would not have become friends if the astrophage threat didn't exist, but I think that all those factors made them made aside a lot of the fears and walls that people (and eridians) can have when meeting someone for the first time.
Simon didn't have that to his advantage.
Like I have said in other of my posts, I think that if Simon is a mutant Grace would be interested in that aspect of him, but he would dislike Simon for been human, since I strongly believe that Grace is scare and repeal humans after he was sent to the Hail Mary. Grace, beside maybe the touch-starvation that he may present (I usually picture him with touch aversation, but you get the idea), has no need for Simon, is more -if we want to make it more angsty- the true is that if Simon appears in their way to Erid, he just means less food for Grace.
I'm not saying that Grace would not give food to Simon, or talk to him, but there would be that wall between them, and maybe Grace would not want to break it. He would be amicable enough to not break a fight, but he would have no real need to go beyond the professional stage. He would not want to be as vulnerable as he is with Rocky with Simon, no when Simon presents too much of a threat for him and bad memory of his last moments in earth.
Meaning that for Simon, Grace would be Dr. Ryland Grace, and I think that could lead to Simon also been scare of Grace, specially if they are in the Hail Mary.
I have see some fan arts and fan comics in which Simon is scare of Grace because he thinks Grace is working with the C.O.I. However, I think that Grace could be scary by his own volution. We are talking of a man that killed the first alien, who also is the only person who knows where the gun and deadly heroin dosis is in the Hail Mary, but besides that I think that Simon would see a scientist who has a lab at his disposition - Simon may know some things, but Grace could be doing a whole new poison in the lab and Simon would have no way to tell this.- and who had control over the whole ship by just saying his name.
I also think that if Project Hail Mary and Iron Lung share a universe and the Quiet Rapture is just the universe that we would have is the project Hail Mary failed, then people would have grow more wary of the scientists, maybe even making them responsable for the Quiet Rapture, meaning that in Eden scientists were saw as this people able to dissapear stars. Simon knows Grace is the savior of stars, but he also believe he is able to destroy them, putting even more tension between.
In this version/AU it is Rocky who is able to interact with Grace and Simon and see who they really are, but it doesn't matter how much he says to Grace that Simon is actually very well mannered, or Simon that Grace is a very kind soul, they would not listen.
Rocky would be working really hard, maybe even with other eridians -as Adrian who as a biologist/zoologist has no idea why the only two individuals of the same species in the whole planet that have a history and biological need for socialization would willingly decide to avoid each other- to make this two humans to grow closer.
