Wait so... okay... lets run through all of it.
Jian finds him. Okay then.
Confronts him, alright.
But then the key thing is such: She knows the air in the syrimge can kill, and claims he's the first person to die by her hands.
This can mean 1 of 3 things:
1. That injection she gave to her mom was an unintentional killing.
2. Possible manipulation of footage.
3. She actually did kill her, as a mercy killing. Less likely, but with the possible lies on display, aint impossible.