So how far are they? To be honest that byakugan range is just something I got from the wiki. There are no info about how large Konoha (or the world) is supposed to be. But this reddit post is the best I could’ve found https://www.reddit.com/r/NarutoFanfiction/s/XInCyttWIH 

Eh..honestly if you don’t want to go into nitty gritty probably just make a GM call whether Hikari can see them or not via byakugan