as far as I remember, yes, sadly. She may have made a small cameo in his (SPOILER, won’t say) later on, but she’ll never be a character again. First you need to question where she came from: a dungeon created by the System. Is it an alternate universe? Or is it...not real? Now that’s only part of the answer, I don’t want to reveal too much
Bluh... Esil is the best, it kills me to see her disappear like that. I don't know if we'll ever see her again, but if not, she deserves her own spinoff series. 😥