What would you do if you had a friend like this?

I have a friend that I have known for over 20 years. We have been friends on and off. When I was 13 she came to my home to challenge me to fight. The were times that she would not keep her word. Other times when we were trying to have a close friendship, she would act funny out of the blue and made me want to end the friendship. She had a non-chalant attitude about our friendship. There were times that she would clearly show her favoritism for other friends. At one point, someone told me that she spoke slander about me. She also use to be reluctant to visit me because I lived far (40 min by train). Now some of her favorite friends have dropped her like a hot potato. We ended up speaking again despite all that happened. Now she wants to act like an ideal type of friend, she wants to follow me like a shadow, and does whatever she has to not to loose me as a friend.she would now visit me even if i moved to peking,china. She even spoke about relocating to the same state I'm going to. I feel funny now because we never really been that good of friends. Now I don't want her getting too close to me. She asked for my new address and I'm reluctant to give it to her, and I'm afraid she would move the new state I'm living in. I have thought about changing my phone number, deleting her from my yahoo friends, and putting her mail as spam. I even thought that if she came to live near me, I would consider relocating again. What do you think is going on here? What is your opinion of this situation?