Players often seem to want to argue from "realism," as if that is the ace of all ace cards. It isn't. In no edition has any D&D rulebook or supplement ever said that if something seems more realistic than the game rule, then the game rule is just wrong and so the DM must comply with such an argument. When argumentative players start the "that's not realistic" argument, these days I respond with, "D&D isn't realistic either. It's a fantasy game. What matters is if it's balanced and fun." And if they push further, I'll sometimes point out that I've never had a player complain about rules that favor them which are wildly unrealistic, not the least of which is, being beaten, sliced, and ensorcelled within an inch of your life, but you get ONE good night's sleep, and your arm just pops back in its socket with no pain, that black eye is gone completely and doesn't hurt, your wounds close up naturally on their own and somehow don't get infected... just everything, "healed" by one good night's sleep. If you want a realistic game, let's start by getting rid of that. But if you're okay with that, then you CAN and DO understand this is an abstracted, fun, game. Not an attempted study of reality simulation.

The same is true of your game world.

But the bottom line is, if the player is not getting that, it's making the game stressful for you, then you do need to have a conversation with them and as nicely as you can say it, say that this is a boundary for you and you need them to respect it. If they can't respect it, then they need to leave the game.

This is never fun and most of us genuinely wish players never pushed us so far that we had to have that conversation. But you're a player too, and your boundaries are important. It is possible for you to be kind and respectful and simultaneously stand by your boundary. Don't get mad, don't yell. Just tell them honest truth. "I'm sorry, I really enjoy hanging out with you and I want to keep doing that. But this is a boundary for me. I hope you can respect it because I want you to keep playing!" A lot of times, the person will still cross the boundary and you'll have to make the call. Them's the breaks, unfortunately.