C229 absolute arithmetic

I walked out of the hotel and got into a taxi. This time, I could return to my dorm successfully, but when I opened the door, I found Cheng Qinglian inside. She was sitting with Cheng Qingwei, watching TV. Why did she bring Cheng Qinglian here?

Obviously, it was unnatural for Cheng Qinglian to see me, and it was unnatural for me to see her