Friendship Troubles? :(?

Okay, this is gonna be kinda long. Okay. Well, I moved to anotehr city in 2nd grade. One girl, I'll call her "Cathy" was very nice to me at first. She took me under her wing, and befreinded me. However, she mocked me a few months after that and crushed my confidence. She was my only friend, b/c Cathy wouldn't let anyone become friends with me. I only had her, and all she did was boss me around and bully me. I secretly hated Cathy now, and to top it off, we had absolutly nothing in common. A few years ago, Cathy moved away to a foreign country temporarily. (about a year and a half) During this time, I make new friends, froiends that respected me and were REAL friends. One of these people was "Katie". She and I had a lot in common, and our parents accually knew each other well from PTA meetings. We quickly became good friends, and I knew what it was like to have a REAL best friend. We were always in teh same cles (the gifted cles for bright students) and I knew her sorta. The only reason we hadn't been friends was b/c of Cathy. We were inseperable, having sleepovers and frequent trips to bookstores together (we are not teh mall types, Cathy is) However, Cathy moved back in December of last year, meaning she was coming in the beginnign of the second semester. Katie and I we closer than ever. Now, let me explain something. Cathy and Katie do NOT like eachother. Thsi was a past history. You see, it is complicated, but Cathy bullied Katie too before i came. They still hated eachother. In fact, they never got oevr it. Anyway, CAthy was suprised I had made a bunch of new friends. She got very jelous, b/c I was her only "friend". She made it a point to critisize me in front of Katie. Katie, thencie eprson she is, stood up for me. Cathy got angry. She started to get close to us, like in lunch, and she was always barging into our convorsations. I know she is jelous. I have tried to be ncie to her, even though we have a bad hisrtory (let me give you an example of Clic Cathy; she told on me to the teacher in 3rd grade and 4th grade for ahem "being too weird") She invited me to ehr house, and made excuses to call me. I think that she was so afraid of losing me before she left, and now she has. I know that deep down she is a nice person (I have witnessed is a few times, she found a satry dog and took care of it, for example) so i thought I could ignite that nice Cathy maybe, and then we could all be friends. i tried to invite ehr over and such about a month ago, and no one ever picks up the phone. I tried emailing her, same thing. I have given up. I am pretty sure she hates me, and she is NOT the type of eprson you want to eb hated by. She is VERYnasty. From the time I met Kathy till now has been over 5 years. Thsi has gone on long enough. I wonder how I can get the ncie Cathy to come out, or how to get rid of Cathy. I think we will probably drift apart, but I have many cles with her next year. What do I do?