They seemed to fight more than they were actually friends.
I'm not here to bash the movie, I sorta like it and find myself watching it when I happen to pass on TV.
But it seems like a flaw to me that for the majority of the movie they are mad at each other and/or fighting. The ratio of mad-at-the-other to yay-we're-good-friends was too much. I suppose we're just supposed to believe they were realllly close and all because they kept saying so? We weren't privy to all the letters, so maybe they got really deep and close in them...more than we ever saw.
And it mostly seemed to be Hershey's character who was the jerk throughout the movie. The time she came back to see CC at the flamingo place...I understand CC initially blowing her off and saying she has nothing more to say to her. Friendships can end. Toxic can outweigh the good and at some point you have to wise up and bow out gracefully. Perhaps that time in Atlantic City was fun, perhaps early years of being a pen pal was fun, but people can still be jerks and bad friends...like Hershey's character was. Even when they were at the beach trip near the end, she was STILL being a resentful jerk to CC.
So...while it WAS sad at the end and all that...mostly, to me, because she was a mother dying young and we knew the kid would have to be alone/without her mom...I didn't really mourn for their 'friendship' because it always seemed competitive and toxic. CC did seem to like her, though, so I felt sorry for that aspect a little too.
I wanted to witness and feel more genuine warmth, bonding and love between them.
(And how was Hershey's character 'the wind beneath her wings?' She seemed to like insulting her and being resentful more than supportive.)