The girl is admitted to a hospital in Bishnah area on the outskirts of Jammu, they said.
Ram Pal, serving in the army and a native of Khadia Kurd village, and Neena Kumari of the same village were in love for the past one year, they said.
Pal had come home on leave and the two took the extreme step on Thursday night and were found unconscious in the fields.
Villagers spotted the two and rushed them to the Government Medical College Hospital.
Pal was declared brought dead while the condition of Neena is stated to be critical.