how can i fix a broken friendship?

Well i hope this isnt getting annoying, but ever since april i have been posting about this girl i like. anyways you probably know what happened over the past few months but im going to say it again just to clear things up. anyway i met this girl at our graduation party back in March, at first she didnt seem like the kind of girl i would fall for but the more we talked the closer we became the more i started to fall for her. then i came up to her and told her how i feel about her, she was perfectly fine with me liking her in fact she even admitted to flirting with me once she knew that i liked her. anyways once school began she admitted to having feelings for me. so for one week we were......well Bf, Gf . then she said she didnt want to be in a relationship cause of her studies and i got kinda sad and she didnt like it so we got into a bit of a fight. a few days later we said we were sorry and everything was back to normal. then after that maybe around 2 weeks later she said she was falling for me again, so for another week both of us were like bf, gf, then this time we both decided its not time for a relationship. so we stopped it although i still have feelings for her. a few days ago i pissed her off(i didnt mean it of course) and she got mad at me, the next day we were all good again, then yesterday i made a joke about cancer and she got offended since her grandfather died of cancer. she got mad again but i kept telling her i didnt mean it and i was so so sorry. and now she never ever been this mad at me, she remmoved me from her contact list on skype and keeps ignoring me, i wrote her an im sorry letter she seems to have forgiven me, but not fully she said she is still not my friend and dosent know if we can ever make up for this. im sorry for the long post but im really scared, and i feel so depressed.......any advice from people who's experienced something similar?, please help