I have to agree, it does seem like Kishimoto meant to cause the reader to doubt Sakura's words. If he had meant Sakura to look completely truthful, he could have done a much more heartwarming scene. But that wasn't how he wanted things to go. He made most of the characters skeptical, including Naruto.
Were most of the characters skeptical?
The only person I think was skeptical was Naruto, and he has since found out that his reasons for being skeptical (holding onto 3 year old memories of Team 7) were wrong. But since the reader identifies with him, that colored the rest of the scene, regardless of the truth.
I think the rest were surprised that she would put a love confession to Naruto ahead of killing Sasuke (*cough*cough*

).
My point is that Sakura doesn't know who she loves yet. That is my interpretation of the manga. She loves Naruto a lot, but she also hasn't dealt with her feelings for Sasuke.
I think she has dealt with her feelings for Sasuke. (That's my interpretation.)
In chapter 458, she started bawling her eyes out when she realized how much Naruto loved her.
Then she opened her eyes in shock, then hung her head in shame, we she thought that she was hurting him.
(So she has had her eyes opened about Naruto.)
In chapter 459 page 10, she tells Shikamaru: "... please... don't say anything more..."
I think that is the moment she finally dealt with what she felt (past tense) for Sasuke, on top of all the subtle changes in Part II that led up to that moment.
What would need to be shown to make you think that Sakura has dealt with her feelings for Sasuke?
(That sounds more combative than I want. This is an honest question.)
Although we know that she will meet Sasuke again, the character of Sakura doesn't know that the story is going to take her there. So a face-to-face confrontation may never come, in her mind.
To shift gears a bit, this would seem to be another reason why NaruSaku feels right. Naruto and Sakura both have strong feelings for the other, but had thought that it was wishful thinking that the other might feel that intensely as well. And when those illusions were broken, they both reacted very strongly: crying. (Naruto didn't cry as much, but he did pass out on top of that).
edit:
Why the confession? We don't know for sure, but it's likely because she felt that if she talked to him as the person he fell for, then it might work.
I have made the argument that she confessed because it was now or never. She believes that hunting for Sasuke will make Naruto hate her (in Sai's opinion), in which case if she waited at all she would never get to confess.
She also put a (slim) chance of happiness with Naruto ahead of dealing with Saskuke. If Naruto had accepted her offer to go back to the village together (and stay there), neither of them would be hunting Sasuke.
Edited by RedDelicious, 04 January 2010 - 03:31 PM.