So Etra has a mediocre modicum of mana and relies entirely on S-tier+ magic items? She's a BS magician? Without those rings she's just a narcissistic lolibaba addicted to gambling? Nhentai, where ya at?!?! Fresh meat for the mesugaki tag.
And thus how Anna has Etra right where she wants her. I spoiled this last chapter comment section, there is no escape for Etra. Anna will work her to the bone until the overtime is gone. And even then still keep working her to the bone for the debt but not as hard. Overtime must be eliminated.