Assuming it's Ren'py:
1. Use
0x52's Universal Ren'py Mod
2. Change names in-game
or
1. Download this basic text file
2. Open scripts in the game to find character variables (m = "mom", etc). You can also use hex codes to set the color of each name.
3. Edit this file to change names of whoever
4. Put the file in the game's "game" folder
Here's the script, if you'd rather copy/paste it
init 999 python:
landlady = Character("Mom", who_color="#f50af1")