I thought that too, but now i'm starting to question this. If they found her dead it wouldn't take long to find out who was the last one in the room with her (last one to see her alive).
Unless he didn't use the OD method. After all that had been done already, on Daniel. He'd need a new method, doncha think? So maybe he did use an undetectable poison which gives symptoms similar to flu symptoms. And one which takes a couple days to work.
I know, i keep bringing up theories that contradict other theories, but you people make some good points and we all just want the truth to come out. So i'm not ashamed to contradict myself.
That has to be resolved. The odds are astronomical. I have to believe it's an undetectable poison that acts very quickly. Most undetectable poisons are administered over a period of time.