I'm losing touch with the best friend I have ever had and I don't have a clue how to cope
How do you feel about losing your best friend?
I feel incredibly sad about this.
I'm sorry your relationship is rocky, but you can't just sit idly by like this and watch it all disappear. If you let your fear take charge, you truly will lose your friend. you need to set up a date with them just to talk about where the two of you are going, to try to save the relationship.
I am worried about how it will go.
You need to make a try anyway. Even if it goes wrong, trying to salvage the relationship is better than not trying at all.