The thing you are forgetting is the first thing Sai says about Sakura's feelings- that she had moved on from Sasuke and has fallen in love with Naruto- in other words her confession of her feelings for Naruto is 100% true, just like Kishimoto said in the Jump Festa in response to the letters he'd received from naruhina shippers going on and on about Sakura "using Naruto's feelings" He said- "On the contrary I felt I was writing her as an honest and surprisingly determined girl." In other words if you saw her confession of feelings for Naruto as completely real you get the prize- you read it right.
As has been said Sai only says something about Sakura having any feelings for Sasuke after Naruto bullheadedly insists Sakura is still in love with Sasuke. Naruto didn't witness Sakura's confession to Sasuke, so he doesn't know even at 13 Sakura knew her feelings for Sasuke were hopelessly one sided. She says so right in her confession- "You must hate me..." When Naruto makes the POAL Sakura's subconcious feelings for Naruto make their first true leap to her conscious mind- her thoughts in response to that promise sound like a girl falling in love... By the time she asks Tsunade to train her Naruto is already on equal level in her heart- as seen by her thoughts and Tsunade's sharp observation. By the time of Naruto's return Sakura's being in love with Naruto already was in place, and even Sakura was conciously aware of a definite attraction to Naruto. You couldn't get a more obvious picture by contrasting how Sakura reacted to seeing Naruto to seeing Sasuke. Naruto was totally oblivious to Sakura's direct flirtation with him (much to Jiraiya's disgust!)
But Naruto overplayed in his mind her reaction to seeing Sasuke. She gasps in awe for a second and he thinks it's love

And in the aftermath of the debacle Naruto comes across as the one in love with Sasuke, not Sakura. Naruto is collapsed on the ground sobbing away about his failure. Sakura is crying but it looks more in response to Naruto's sobs, she's mostly in control of her emotions and her words as well are all about being there for Naruto. Look as well to their reactions in the aftermath in Konoha. Naruto is feeling hopeless heartbreak on a bench, Sakura is in the library researching what chemicals could have made Sasuke become so fast and powerful. She's calm and determined, and already certain enough in her feelings of love for Naruto to flirtatiously tease him about what her nickname for him is. Naruto again is oblivious and misses the flirting tone and her mischievous flirtatious smile.
Sakura's lingering feelings for Sasuke is of a person she knows he'll never be again- 12-13 year old boy on Team 7 that she had a one sided crush on- the boy who's dark impulses were countered by the influence of Naruto, a boy who let himself believe for a short time that maybe this Team 7 stuff was worth anything. Sasuke's parting words to Sakura tells you that.
Edited by ciardha, 10 January 2010 - 08:08 PM.