Wow. We're gonna get along great!
I had the EXACT same problem (and I still do from time to time). I'm assuming your coach is still spotting, right? That always reassures me. I think part of it is trust, in yourself AND your coach. You have to trust yourself to let go, and you have to trust your coach that he/she's; a, not going to let you hurt yourself, and b, he/she's not going to let you do it if you're not ready.
As far as getting over the fear... visualization helps. If you can picture yourself doing a perfect flyaway, you'll do a perfect flyaway. You just can't visualize anything negative, that's the key.
The other thing that helped me was starting with them on the low bar. Swing with your legs tucked, then on your third swing, let go and have your coach catch you. That way, you're getting used to letting go without flipping, AND you learn correct timing. Once you master that, do the same thing with the flip. After that, move it up to high bar on the lowest setting. As you get comfortable with it, move the bar up. You'll find yourself getting used to it.
Also (jeez my finger hurt from all the typing!), I'm sure as of right now you're scared to swing hard into it, but the bigger the swings, the easier it gets. And the more height you get, the less scary it is.
One more thing; you just have to get yourself to do it. Work up the courage and believe in yourself! You'll get it eventually. It may take time, it did for me, but I have it now. And I know you will too.
PM me if you want to talk at all! I can completely relate to your situation. I actually got to the point where I thought about quitting because of it. Don't let it get that bad. Remember; part of gymnastics is going to be fear, but think of how great it will feel the first time you're that scared but you do it. I've never had a prouder moment than when I did my first flyaway by myself (and that was just a month ago! We started working them in November! Hard work pays off, my friend!

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Good luck!!!!!
-xoxo
Kayleigh