I Suck At Maintaining Relationships

My one friend (who was a senior) and I had a kind of rocky relationship to start. For just under two years we were really good friends. Because of an extraneous figure outside of our relationship my friend and I got into a fight. We ended up not talking for a while. After a few months, we apologized for everything that had happened. We became closer than we ever had been and I actually think that I started to develop a crush on her. Her and I had gotten closer, physically than my ex-girlfriend and I did within the first month of our relationship. It was just different. After the school year ended, we hung out for the 4th of July and that was it for the majority of July. I was set on the fact that she was moving on and that I was going to have to learn to live without her because she was going to college. There were even times when we'd be at the same place and she really wouldn't even talk to me. It was like we had become strangers after being closer than ever and that happened so fast. One day two weeks ago they took our best friend to the hospital because of an issue that she has had and that was when we kind of started talking again. We were both scared and worried and anxious about everything and from then on we've done so much together. We've hung out a bunch and now I'm feeling that feeling again of maybe not a crush but just remembering how important she was to me. She's leaving at the end of the week and I don't know what I'm going to do without her. We were friends, then we didn't talk, then we got super close, then we weren't, now we are and she's leaving... I'm kind of screwed.