While Sakura was indeed annoying in Part 1, she definetely became a better character in Part 2. Her not fighting against Pain, is in no way a bad characteristic of her, and really, the only one who tried saving Naruo was Hunata, so you're speaking bad of the whole village. Also didn't she lie to Naruto, because in order to help him forget Sasuke, or something, i can't really remember anymore. However, of course Kishi had to ruin her again in the World War, when she became obsessed with Sasuke, so i guess that she didn't really become much better in the end...