Well nevermind, not a good idea to mess with those strings/variables hehe. Well seems you have to change in the code like you said, what files, no idea and even that way seems a bit messy and too much work even changing all that says "Carmen" to any other name. Just better to ask the dev to add something to change the names but usually they only do it for a few characters and most of them only can change the MC name.
But that is the mod I use in all renpy games, to look under the hood and change/cheat a few variables if need, saves me time like doing a whole fresh playthrough just to change a variable to false to true or vice versa, and besides that has many other features, it is a "mod yourself" rpa file that goes into the game folder and that doesn't mess saves because doesn't overwrite any game file. but its here, there is a thread in this forum for URM
Mod - Ren'Py - Universal Ren'Py Mod / URM [2.6.1] (mod any Ren'Py game yourself) | F95zone | Adult Games | Comics | Mods | Cheats .
Edit: its says on URM page OP "rename any char" and in the list of features but probably need to be careful to what you need to change, I tried a few fields and then kept giving me not defined errors, gladly I just had to put the original thing that was on the field changed and the errors were gone, my worry was that it "infected" the persistent file and then would be annoying. Also the name appear in several places, in the dialogue, when the character is speaking in bigger font, in the bios screen etc etc, usually is an hard endeavor. You can always ask in the URM thread how to do it.