Valmiki Ramayana Aranya Kanda Sarga 32 Shloka 3
Original Shlokaसा दृष्ट्वा कर्म रामस्य कृतमन्यैस्सुदुष्करम्। जगाम परमोद्विग्ना लङ्कां रावणपालिताम्।।3.32.3।।
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सा she, अन्यैः by others, सुदुष्करम् very difficult to do, रामस्य Rama's, कृतम् done, कर्म deed, दृष्ट्वा after seeing, परमोद्विग्ना getting very scared, रावणपालिताम् a placed ruled by Ravana, लङ्काम् Lanka, जगाम went.
Seeing the performance of Rama which is very difficult for others, Surpanakha got scared and went to Lanka, ruled by Ravana.