I wouldnt worry about your “BFF” stealing guys from you now that you are moving away from her.
And your situation isnt quite a catastrophie. Youre in middle school, horomones are bouncing off the walls and quite frankly, there is nothing you can really do about a guy who wants to date you if you are moving away.
Focus more on Christ and less on boys and you will see that your problem is actually quite small. Let Him deal with your heart and your emotions.