So I have a theory and its kind of dark. So by this point I have listened to all of the books enough times that I might have a bit of an obsession. However, the last two or three times I've listened to book 2 I've been getting the sinking suspicion that Sabine was simply used by the owners to get Jack. I've thought about it a lot recently and I really wanted to just lay it out here so I could get others opinions. I think the best part to start for me is consider the owners first from a supernatural point of view. At this point in time I'm pretty much convinced momma and pops were more then human, so it always strikes me funny when Jack uses Sabine as evidences of the humanity. So this leads me down the Rabbit hole of what is Sabine if the owners are not humans. This lead to a depressing theory in my head that she was a creation of the owners to secure Jack.
I believe that Jack is like Rosa, not as in just like her I don't think he is a host, but I do believe that he is a unique human. Unlike other people on this blog that theorise he's demi divine I believe he is just an extraordinary person with unique supernatural abilities. I believe that this is why memory magic doesn't effect him and his ability to not sleep is also part of it. Anyway, my point is he is uniquely well suited to be the gas stations night manager and the owners may very well have know this when he was young. I Believe Sabine was some sort of creation of theirs to ensure that Jack would work for them, Just like they would burn down a building to ensure they had Rosa on the Pay roll they were willing to make jack fall in love to get and keep him on the pay roll.
I believe this is why Sabine never attended a real school, and why she was in such close proximity to Jacks first foster home. She may not have had the documentation to be enrolled in a real school due to her not having any record of natural birth. However, I believe I'm grasping a straws here as the owners are resourceful enough to acquire those documents.
Finally, I think owners were behind the crash that put Sabine into a coma. Sabine was useful for keeping Jack in town and working at the gas station, therefore was an asset for momma and pops. When Jack received his diagnosis she shifted from being an asset for the owners to a problem. She became the driving force for her and Jack to escape the town while he still could and well the owners solved that problem. After the crash jack became depressed, he fell into the routine of working at the gas station and had no ambition to leave.
Please if I've missed something let me know, and if you think I'm just a Debbie downer also let me know.