go to the top of shushuya and if she isnt there warp to another map until she appers
before you fight kakashi in the final fight or ultimate road go find her and help her with what she needs. then after you fight and go through naruto being the hokage go back and look for her again then you have to go eat with her then you got her.
OK. When you move to Kohona go on the roof of the Shushuya resturanunt thing. To get there (From starting point when you get there) Go up and take a right at the first building, then take another right, then jump and your there. She appears every now and then, so if shes not there, move to another place on the map, and go back to Kohona and see if shes there and repeat.
I think it is still possible to get Hanabi and the other characters after Story mode because you can still get jutsu's afterwards, so try to follow the advice even though most of us probably used that advice before we finished story mode....myself not included^^