Generally most would be told to make the letters fatter but I suppose that is not the goal here.
Short version. Probably not. http://bgb.bircd.org/pandocs.htm#vramtiledata
The GB/GBC setup makes this harder than some later systems as things are more geared towards being 8 pixel aligned than later things where BG tile placement and size is almost arbitrary. Depending upon how much text you have (big RPG is harder, puzzle game probably easier, don't know if that is a visual novel which can go either way) some go for letter pairs (or letter and a half). Other times people instead opt for maybe using the sprite options instead where you can stuff up to 10 sprites per scan line, though that still means difficulty in getting characters on screen.
Anyway if the game does not have an internal width value, or maybe spacing value (rare for Japanese games even today, never mind on the GB/GBC), then you get to play with the text handler in the game to do it. If you already edited the font to have the thing accept it then it would usually have been around that in the game. Otherwise a tracing session that follows the game's text being fetched, the corresponding tiles being fetched (doubt they are all in VRAM all the time for a GB/GBC game, especially not an originally Japanese one) and then placed on the screen being what you want to look at.