How Do You Confess Platonic Love?

I have a friend who is going to move out to the mainland. How do I confess her know that I wish she is my sister? Will it sound like a creep? If so, how less creepy? After all, I am a guy. Cross-gender friendship is difficult, especially there is misinterpret sexual tension involved. You know, look like I am hitting on her, but in reality, I really care for her as a great friend.