Should I go say say to a friend that I hate her?
Why do you need to tell her you hate her?
There's a major reason behind it
Whatever the reason you have for hating her, it's very hurtful for you to tell that to her face. You need to prevent that from happening by just telling her what she did wrong. Your friendship isn't worth breaking up over a simply word of "hate".
I'm only doing it as a experiment.
But she's your friend, isn't she? Do you really worth quenching your curiosity by risking your friendship? How do you think she would feel that someone she is close to suddenly betrayed her?