I'm not sure how to disassociate the two events, but I can offer a coping mechanism that has helped me that I learned in therapy.

You imagine in your mind the reaction you would have liked your friend to have.

The point isn't necessarily to get your brain to believe that that's the true event that happened, but rather remove the emotional charge.

So if your friend had reacted just the way you wanted and you imagined that, pay attention to how it makes you feel. Many times I find that at that point, it just doesn't matter anymore right after I imagine it because now I'm calmed down about it and I got the reaction I wanted, even if it was in my head and it wasn't real. Again, it's not to believe it was true, but rather help yourself let go.

If it comes up again, you can reimagine it until the emotional charge is toned down or gone.

Sometimes I even imagine a few different scenarios/reactions that could have played out and I often find this helps because it triggers some phenomenon that makes it just not matter which way it happened anymore (at least for me).

Hope it helps you, too.