Friend talks too much, how can I tell her?

Your friend sounds like she may be manic-depressive. You have no choice but to tell her, unless you no longer want her as a friend. You could say it in a joking way, such as something like, "Hey, hey, pipe down, you are always talking a mile a minute!" Say it humorously, with a smile on your face. All you can do if she calls you too much is to screen your calls.