I interpreted this as Sakura not trusting Sasuke and not liking that he's here but she's trying to shield everyone but her and Naruto from the situation.
He is their teammate and his behavior will have to be dealt with by them. Saying anything but what she did would just attract attention to the situation, hence her lying to Sai about how she feels and Shikamaru's lying to Ino about the situation even though he knows what's up.
Sakura lied about being happy to see him and trusting him because it's no one but hers and Naruto's issue. Mostly Naruto's since she accepted his decision to let him handle it.
He is their teammate and his behavior will have to be dealt with by them. Saying anything but what she did would just attract attention to the situation, hence her lying to Sai about how she feels and Shikamaru's lying to Ino about the situation even though he knows what's up.
Sakura lied about being happy to see him and trusting him because it's no one but hers and Naruto's issue. Mostly Naruto's since she accepted his decision to let him handle it.