How can I tell a friend that I don't like them anymore?

When I went into 6th grade I met this really nice girl. She soon became my friend. But, as the year went by my friends and I started liking her less and less. She said she was going to move states and we were very happy but now she isn't! Last time I saw her, I slept over at her house and she told me she liked my boyfriend! I want to be gentle next year when I tell her I don't like her anymore but I just don't know how! I need ways to tell her that wont make her feel to bad. PLEASE HELP AND HURRY!!!!! I need something to say before school starts again!