It's like this, what she said could have been completely true, but her face says otherwise. What she said is more like something she wish to say with a complete face, but we know now that she's with everyone else: don't trust Sasuke. Sasuke has another agenda, but he won't reveal until well, Madara is out. We got a glimpse but that's all. Kishimoto clearly wants us to see it as a sign what's to come in the future. Even Orochimaru is waiting to see how Sasuke will execute his "wind".
I think this is too complicated, the purpose of Sai observation wasn't to tell the readers that what she said was something she wanted to believe, it's clear like water she wasn't being honest, does this have anything to do with her feelings for Sasuke getting weaker? Does it has anything to do with Sasuke's attempt of her life? Or doesn't it has something to do with her sensing some conflict between Sasuke and Naruto knowing that a fight could remember her what Naruto said to Sasuke back at summit? It could be reason one, two reason or the three of these reason might be bothering her regarding Sasuke but because she doesn't want anyone to start going against Sasuke at this time and they sure need his help she needs to pretend that everything is OK for the alliance and maybe for Naruto's sake after all he said that he will take care of Sasuke not the Rookies.
The only thing I'm regretting right now is not seeing Sai asking Sakura why is she lying about trusting him, what made her change her mind about him?
Edited by Don-kun, 27 June 2013 - 11:30 PM.