@Abedeus well, I assume that the author started this as a comedy manga with a simple setting, and decided after it got axed that the ending should explain the whole setting and had to quickly make up some plot for it. It's not like the ending / Marom is the only bad writing in this series; the motivations for a lot of the characters are flaky at best.
The divine protection literally revives dead people and does allow them to keep all of their memories, so the tech (or rather, magic) exists. Of course the author could invent another reason for why the healing components of the divine protection won't work for Marom, but at this point it would just be the bullshit-frosting on the garbage cake. To create immortality you have to find ways to stop your cells from degenerating - so why does her brain still degenerate if the rest of her body doesn't? The simplest explanation for that is that the author is braindead. Would you accept it if instead of dementia she would be suffering from MS or ALS?
The "teleport medicine into your brain" part was just pointing out the smaller plot holes on top of the big plot hole. I can think of at least 20 better ways for a mage to take medicine than doing it in literally the same way than a normal human person. She could have a magic servant or tool that feeds her pills when she has an episode, make an auto dispenser spell (exchange some air in stomach with pills every hour), whatever. Not that it matters because it's retarded that she has this illness in the first place.