I know, I am probably poking into a subject that really has no relevance at first, but there is a point to it.
I think Sakura is mature enough to understand Naruto. Again, look at what she did during her confession. She tried to take matters into her own hands knowing what will and could happen in the future. She wanted to protect him at all cost. The fact that she was willing to understand the situation and come to conclusion show that she understands Naruto...if he told her stuff. That's the big issue here I feel. It's not that Sakura understands or not, but rather what is Naruto willing to share with people. He refuses to tell people his biggest secrets and wants for one reason or another. I am not even talking about his nindo either.
Naruto is such a closed off character to the rest of the group. It's funny given that he wanted to be part of the group in the beginning, but by now he pushes his way out of it for fear of others getting hurt or getting caught in the cross-fire. Thus he tries to be selfless. Eventually, this makes Naruto very stubborn. No one is allowed to help him in anything. People understand Naruto just fine, but Naruto refuses to let people in to his world despite many telling him he needs to let people in.
I think this is where Itachi comes in. Itachi is very intelligent. He knows what it is like to be that way and I think he saw this in Naruto. Does Itachi understand Naruto? Only in one aspect I believe. I don't think he knows Naruto as a whole otherwise he would have given him more advice.
How many other people know that Naruto loves Sakura? From my count one. Sai. He saw it in Naruto from the mannerisms he portrayed. Many people ignored it or didn't bother to mention it. Sai saw how Naruto was trying to tell Sakura how he felt, but Naruto refused to tell her because he was insecure about himself. He was insecure because he didn't believe he deserved it. So Sai took it upon himself to make the move for him, but again this is only one aspect of Naruto.
I think Sakura knows and understands everything about Naruto. She knows he has a nindo to always protect his friends and she also knows that he is always trying to take on the world by himself. She also knows now that he has always loved her and that he is insecure about telling her.
This is the most complex of it all. Chapter 573, again, I still stress is a very important chapter because you can see Sakura make a choice to not falter anymore. She says "We're going to be together no matter what you say." She knows that Naruto will deny her into his life, but she is going to stick by him no matter what because she knows Naruto will try to keep pushing her away.
Naruto knows that Sasuke is the last challenge. This will affect both of them and it is almost similar thinking to what Sakura felt during her confession. She wanted to take on Sasuke herself so Naruto didn't have to knowing full well it will break his heart. Reverse for Naruto. He did it so Sakura doesn't have to and she can hate him if she must, but he accepts that. This is why he doesn't act the same way to Hinata or push her away. Not because he loves her, but because she has no connection to Sasuke what so ever. Hinata doesn't care if Sasuke lives or dies. Only how much it affects Naruto.
Sakura....she understands alot more than she puts on. She has secrets too that no one knows and Naruto is going to be surprised by the end of it all.
Edit: Fixed some errors and rewrote some things
This, nuff said.