>>22502500She probably rationalizes that it's still cheaper to live at home where her parents cover all her expenses than to move out on her own. Especially when she's basically a child still and doesn't know how to do anything herself due to her parents focusing 100% of their time on her brother and not raising her at all.
What she needs is someone like Pomu or Nina or even Rosemi that can take her in and teach her how to be an adult.