Best fake friend

I have a best friend that is actually always with me. She's so funny, loving and most of all loyal! I never thought she would be my sister. I mean she's like my sister. We had so much fun together! Also, we have a secret place where we tell stories to each other about what happened in school, weekends and many more! She always makes me happy! But I never thought she would change. Do you think our "friendship" would last forever?