Canto 2 -
Ayodhyā-kāṇḍa
Chapter 8: The Conversation Between Kaikeyī and Mantharā
Text 2.8.3
मनसा प्रहसामि त्वां देवि दुःखार्दिता सती।
यच्छोचितव्ये हृष्टासि प्राप्येदं व्यसनं महत्॥
manasā prahasāmi tvāṁ devi duḥkhārditā satī
yac chocitavye hṛṣṭāsi prāpyedaṁ vyasanaṁ mahat
manasā = in my mind; prahasāmi = I laugh; tvām = at you; devi = O goddess; duḥkha-arditā satī = afflicted by pain; yat = when; śocitavye = you are meant to be unhappy; hṛṣṭā = happy; asi = you are; prāpya = having encountered; idam = a; vyasanam = calamity; mahat = major.
O goddess, having encountered a major calamity, you are happy when you are meant to be unhappy. Afflicted by pain, I laugh at you in my mind.
According to Mantharā, Kaikeyī had encountered a major calamity—Rāma’s coronation—and therefore she was meant to be unhappy about it, but instead she was happy about it. Therefore, Manthrā was afflicted by pain and so laughed at Kaikeyī in her mind, just as one would upon seeing his master gone mad.