That's really hard.
She just decided to leave? What was her excuse? Did she say that the "magic" in your relationship has fizzled or something of that nature?
She should be more than just a best friend. She is the woman you love, the one you took a solemn oath to never part with until death rips that bond away.
She took the oath, too when she said "I do,". For her to walk out on you like that, without any excuse at all, is sinful and disrespecting God's will.
Women are so emotional, she might show up at your residence within a few days time anyway. Women have this "need" to be protected. If she has noone but you, she will be back.
I'm sure she misses you. Good luck, and I hope all turns out well. Hang in there, pal.