Of course it's normal!
You wouldn't be human if you didn't want to!
Try and look at it like this, SHE betrayed YOU.
She Shagged your H behind YOUR back. (we'll come to HIM in a mo)
You can give her filthy looks, the evils, you can even shout at her, "Yeah, you, keep walking... there'll be another Kerb crawler along in a minute!"
OK, perhaps best not shout out loud, but you can think it.. If you are anything like me, it'd telegraph from my face anyway....
Tell yourself the following:
You will bump into her one day or another, but you will not throw yourself with claws out toward her neck, oh no, you will give her a "who stepped in something nasty?" look up and down and keep walking by, you will be cool, you will be calm, you will not crack.
WHY?
Because HE CHOSE YOU.
And she knows it.
Now, HIM....
He better do some serious grovelling, counselling and general making up. He has damaged your trust in him, and may never fully recover it, but he has to try.
Every. Single. Day. Of. His. Life.
Get some couples counselling, open up and talk to one another.