Did it go into why she attacked Eumi at all?
Cuz given how Eumi looks to her I can take an explanation of not being able to differentiate between one mass of darkness clump vs another and shoot Eumi without realizing it.
But if it's just straight up 'u die now' backstab after all the...friendliness? recently it feels out of character.
LN heroine is simply your usual idiot heroine. she tried backstabbing FMC with trio idiots "in demon lord castle in demon lord subju quest" cuz in fairy tales she loved, black haired is a witch and should be purged and she choose that place of all place to pull her stunt, then surprised when demon lord intervenced