Friend Complicated Things Help Please!?

Ok, so... me and my best friend were exchanging passwords the other day randomly. i told her mine, and she said she;d tell me hers if i never used it. i said i wasnt going to. i tried to log (she knew i was going to do that, just not send a prank email is what she didnt want me to do) and i couldnt. i tried to write her password down but i didnt try it anymore. then, today, my parents, who are getting divorced (my friend knows), had a huge fight with me and both of them. i was crying and messing around on the computer when i saw the slip of paper. i was bored and i tried to log in and it worked. i saw an email from another one of my friends to this friend and clicked on it. they had set up plans without me and i felt so bad. i logged out and then logged into my account, and wrote an email to my friend, letting slip about the plans. then, my friend changes her email password and says i am untrustworthy. i feel horrible and nosy but im so upset and embarrassed. wat should i say? wat should i dO? im so messed up right now. Kelly age 12