Why do I keep thinking of not too talk to her anymore?

Well I'm friends with this girl we get along really good. Now when I listen to the song "It Was Written In Blood" by Bring Me The Horizon it starts out good bye my friend my love your in my heart it was preordained we should part. Anyways that part I imagine myself telling her that. Right now I'm having these thoughts of telling her good bye. Why does this keep happening to me? By the way I had these feelings like last September I remember when I talked to her it seemed like she had been trying to avoid me. Then one day at a church meeting she waved at me I didn't even wave back. Then she started hanging out with me honestly I wasn't satisfied her being with me. Then after we got along good then we got along really good like I said in the beginning. Now I keep thinking of telling her good bye forever.