What should I do if my best friend Starts to treat me differently?

[manne]

So I had this good friend of mine, we were really good friends in the last two years of high school, but about 3 months ago she started to act funny, and keep her distance from me. She would then make fun of me and I found out she talked about me behind my back. I thought this was so strange because for the last two years she use to be so nice to me and she would like my profile picture, facebook statues and invite me over to her house. But then she changed and now she snickers at me, calls me awkward, and makes fun of me behind my back. On top of that, I am moving across the country in 2 months because of my father's job and I will be leaving her behind. I asked her why she was mean to me, and she responded "What did I do now?" "You need to grow up and not act childish." I was so hurt and still am, because I thought she was my best friend.