Shloka 2.37.23
अयोध्याकाण्डे सर्गः ३७ — चीरधारणं, सीतासंकल्पः, वसिष्ठोपदेशः (Bark-Robe Episode and Vasistha’s Admonition)
न गन्तव्यं वनं देव्या सीतया शीलवर्जिते।अनुष्ठास्यति रामस्य सीता प्रकृतमासनम्।।2.37.23।।
na gantavyaṃ vanaṃ devyā sītayā śīlavarjite | anuṣṭhāsyati rāmasya sītā prakṛtam āsanam ||
O Kaikeyi, devoid of good conduct! The noble Sita need not go to the forest; instead, she shall occupy the throne originally intended for Rama.
You are devoid of good conduct, O Kaikeyi! Divine Sita need not go to the forest. Remaining here she should occupy the royal throne of Rama.
Vasistha uses the term 'śīlavarjite' (devoid of good conduct) to reprimand Kaikeyi for crossing the limits of propriety by handing bark garments to Sita, who was not bound by the exile vows.
According to Vedic Dharma, the wife is the 'Ardhangini' (half the soul) of the husband. Since Rama was exiled but his soul (Sita) remains, Vasistha argues she has the spiritual and legal authority to rule in his stead.