I have been there. I was kicked by my last horse. I was leading her through a gate, and let her go without turning her head back to me. She jumped away and kicked out with both hinds, and caught me on the chest and on the chin, and broke my jaw in two places. I understand the fear that you have now.
For me, the way to get past it was to accept that I was in the wrong. Not because she kicked, because that was just her being a cow. I was in the wrong because I put myself in a position where she could kick me. From then on, I have never been in that position. I am VERY conscious of where the horse's butt end is, and make sure I am never within kicking range.
Don't sell her. It is easy enough to get past it, you just have to get past it. It is terrifying, and believe me, I understand that. My kick was five and a bit years ago, and I haven't gone past a horse's back end without thinking of it, but it makes me safer to always be thinking of it.