The reality was that Liu Qi and her visibly disreputable friends shuddered as well when they saw the marks on Qing You.
No ordinary person could push through such severe injuries, true, but what did it prove?
From Liu Qi's point of view, her younger sister was back to fight for her brother and father's love. Since Qing You came back, Liu Tie saved everything nice for Qing You; he pampered her to the best of his ability, afraid that she was even a little bit hurt.
The truth of Liu Tie's indulgence to Qing You, actually, was because he felt that his daughter must have suffered a lot out there during the years she was taken away by the human traffickers and he was at fault for not looking after her well back then.
On the other hand, Liu Qi had no feelings for her sister, Qing You. When the latter was abducted, Liu Qi was only about 10 years old. She was only one year apart from Qing You.