For all you know, the seal would have needed to reach "full" capacity to be released. Of course, sakura could probably continue to store more chakra beyond that point, but that is the point in which she can release the seal. Besides, Sakura's intelligence level is most likely higher than yours. Even I had trouble figuring out the test problems in the chunin exam and she was rocking through that test. Admittedly, they only showed one specific example I think. By intelligence, I meant that if she could have released it that early, I think she would have released it before half of the shinobi's alliance died... There was also the constant danger of being killed during war, so it WOULD have been better to released it earlier, for her sakes.
Hinata's action can be considered as "stupid" or "brave". I'm going with the former. She was hopelessly outmatched. She is a close-ranged fighter. Her speed is average. Her opponent is the Akatsuki's leader. Her opponent's visual prowess surpasses hers. Her opponent managed to pinned down a sage mode Naruto. The least she could have done is come up with a plan and gather some people close to her.
Hinata aside, Sakura proved herself. She lied to Naruto because she believed it would save him. The kid was phucking stubborn. I don't think "Hey, Naruto, don't chase after Sasuke anymore, ok? Bye!" would have been very effective. The act itself is bad but the intention behind is good. Even if that was considered a negative thing in her overall consideration, her breaking off the horn of "the origin of all chakra" is pretty redeeming...
