Why is my friend acting so distant about me going away?

Sounds like she wants to be your BF but you mentioned she will put a guy before you.I think that is the problem.She is looking for a best friend she can share her life with and you are looking for something she knows she cant give you.She feels like the friendship is more than that on your part so she is backing off.If you really want her as just a friend and nothing more let her know that.It might make all the difference.Good Luck in your new job.I hope it all works out for you.