quick google search says she's heavily implied to not be real/a recreation of a demon long ago, i.e. already dead
Wiki says otherwise
"She soon returned in the revised timeline in the Demon Realm, being the last Demon Noble and becoming allied with
Sung Suho, aiding him like his father. Esil would succeed the former Demon King,
Baran, becoming the
Monarch of Gluttony."
