Sītā-devī considered Śrī Rāmacandra’s words to be of thoughtless resolution, that is, absolutely without any substance. This is why she considered them to be due to His thoughtlessness: even she, a woman, laughs at them.

“What are You saying?” indicates that Sītā-devī wanted to point out that His words were unprecedented; she had not come across such words from Him till then. She refers to Him as a nara-varātmaja (“Prince”) to point out that it is impossible for Him to talk to her like this.¹ She implied that His instruction to her to be there [in Ayodhyā] when He had gone to the forest for exile was not a sign of His love for her.

NOTE. The scriptures state that a disciple should not address his guru by name nor can a wife address her husband by name: guror nāma na gṛhṇīyāc chiṣyo bhāryā pater api.²

So why is Sītā-devī addressing Rāmacandra by name? The answer is that this is an exceptional situation because her husband is the Supreme Personality of Godhead who wants everyone to address Him by His holy name all the time, as noted by Lord Caitanya Mahāprabhu in Caitanya-caritāmṛta (Antya 7.103-108):

eka-dina bhaṭṭa puchila ācāryere
“jīva-‘prakṛti’ ‘pati’ kari’ mānaye kṛṣṇere

One day Vallabha Bhaṭṭa said to Advaita Ācārya, “Every living entity is female [prakṛti] and considers Kṛṣṇa her husband [pati].

pati-vratā hañā patira nāma nāhi laya
tomarā kṛṣṇa-nāma laha, — kon dharma haya?”

“It is the duty of a chaste wife, devoted to her husband, not to utter her husband’s name, but all of you chant the name of Kṛṣṇa. How can this be called a religious principle?”

ācārya kahe, — “āge tomāra ‘dharma’ mūrtimān
inhāre puchaha, inha karibena ihāra samādhāna

Advaita Ācārya responded, “In front of you is Lord Śrī Caitanya Mahāprabhu, the personification of religious principles. You should ask Him, for He will give you the proper answer.”

śuni’ prabhu kahena, — “tumi nā jāna dharma-marma
svāmi-ājñā pāle, — ei pati-vratā-dharma

Hearing this, Lord Śrī Caitanya Mahāprabhu said, “My dear Vallabha Bhaṭṭa, you do not know religious principles. Actually, the first duty of a chaste woman is to carry out the order of her husband.

patira ājñā, — nirantara tāṅra nāma la-ite
patira ājñā pati-vratā nā pāre laṅghite

“The order of Kṛṣṇa is to chant His name incessantly. Therefore one who is chaste and adherent to the husband Kṛṣṇa must chant the Lord’s name, for she cannot deny the husband’s order.

ataeva nāma laya, nāmera ‘phala’ pāya
nāmera phale kṛṣṇa-pade ‘prema’ upajāya”

“Following this religious principle, a pure devotee of Lord Kṛṣṇa always chants the holy name. As a result of this, he gets the fruit of ecstatic love for Kṛṣṇa.”