The whole timing does not make sense.
Olenna grabs poison from Sansa, and walks back. If she puts the poison in the chalice, it would be gone when Joffey dumps it on Tyrions head. If she puts the poison in the carafe, it would risk killing her granddaughter. And, when Tyrion fills the chalice, he get the wine from in front of Cersei - so from a filming sequence, I dont see how Olenna could have put the poison in the wine without someone seeing it.
Olenna grabs poison from Sansa, and walks back. If she puts the poison in the chalice, it would be gone when Joffey dumps it on Tyrions head. If she puts the poison in the carafe, it would risk killing her granddaughter. And, when Tyrion fills the chalice, he get the wine from in front of Cersei - so from a filming sequence, I dont see how Olenna could have put the poison in the wine without someone seeing it.