Actually i dont think it was rape at the jail .that time poison of love fury became more powerful so they need to intimated as Susu also lost the poison detoxifier. At first Tantai jin wants to kill her but she request him to save her. Here is the quote ..
"She thought to herself, I can’t…… just die like this, I must live no matter what.
Trembling, she held the hand of the person who had come, tightly clasping his ten fingers, her nails almost digging into the back of Tantai Jin’s hands.
“Save me……”
The young girl trembled in his arms, his fingers bled from the scratches from her nails, and there were even a few gashes on his skin.
He was silent for a long while, then closed his eyes and laughed out loud, “You too……”
The young girl trembled and hugged his neck."..The dim light of the night shattered before her eyes, and Su Su gasped for air.Her fingers hurt, everything hurt. The fear of failing the mission and the pain from the Spring Knot Silkworm made her tremble like a little beast.
Tantai Jin’s fingers ran through her hair. She was like a climbing vine, absorbing nourishment to try and survive from his body."
..................................
He held her hand, kissed her lips, and easily pressed on her aching finger bones.
“Does it hurt? It can’t be compared with the pain in my heart.”
How I wished to kill her, but I actually chose to let her live."