Best episode ever![]()
So happy... Damn I'm happy!
You must be messing with us xD Watched it few times and can't see the exact moment when she adds anything to his cup or whatever (unless you mean that Olenna takes the gem from Sansa's necklace). But indeed everything seems so suspicious - Margaery puts his cup so close to Olenna and there is so many close-ups on her that she indeed seems like an important person in this episode.
On the other hand Sansa had her chance as well when she picked up the cup under the table but I am not sure if she'd be able to do such thing.
<SPOILER>
Ser Dontos (the fool who gave her the necklace) was in on it with Olenna. They used the Necklace as a way to smuggle the poison into the wedding [1] Olenna then grabs a gem containing the poison off of the necklace and places it in his drink (the drop isn't visible in the episode but it can be assumed). When Joffrey dies, Ser Dontos tells Sansa that it is the time for her to escape, which was also a part of the original plan [2]. Unluckily for Tyrion, however, Joffrey decided to get revenge for that awful gift by tormenting him for the entire affair - causing him to look like the prime suspect.
[1] The reasoning for this goes unexplained as of now (and I've heard from book readers that it's not explained in the books, either), but I have a theory. They could have coated the gem with the poison and did it in this fashion as a way to frame Sansa for his murder. Because they were already going to help her escape [2], they could frame her (The Lannisters hate the Starks anyways), get out clean, and get her out alive and without any questions as to why she ran.
</SPOILER>
Except poison, bitch!