From what I understand, in Japan, it's considered unfair to fall in love with the same boy that a friend of yours already loves.
Usually, though, two girls who are friends will take on a friendly rivalry, decide that whoever wins the loser has no hard feelings (of course this never works out), and go from there.
This dynamic played out almost exactly Ao Haru Ride. The main female protagonist agonized over the fact that she loved the same boy as her friend, but came to terms with it by being honest about her feelings.
What does Naruto value above all else? Honesty.
Think is I've never seen Hinata and Sakura as friends. Sakura and Ino? Sure. But Hinata and Sakura have mostly just been shown as classmates, and later co-workers. I'm sure she doesn't hate Hinata, but I don't see why she would sacrifice her happiness for her. Character wise it makes no sense, much like a lot of this manga.