I am sorry for your pain and triggers.
I don’t think your triggers are unfounded but are on a massive level. But start with the friend group.
I agree it is best to avoid them (because of one person). If it upsets you - you have to do what you need to do. Until you get the courage to be able to manage your own feelings and still be able to see her in a social setting, it is best to avoid it. And if you never change your mind about this "friend", then don’t see her again.
Now for the second part. Attractive women who are friendly and possible just doing their job. People get paid (like tips) to be nice and friendly and provide a service. To them, your H is nothing more than the average Joe that they want a tip from.
I’d bet most are NOT interested in your H.
But that doesn’t do anything for you or your feelings.
Just as a backstory my H’s last OW was 20 years younger than me. She was cute enough and he planned to D me to be with her. She was single w/ no kids and ready to replace me (even as a step mom lol).
I worried all the time about all the women out there until I had a thought. My H had an affair w/ the OW because she was available AND willing to be the OW.
She could have been anyone lol. Young, old(er), thin, heavy, pretty, smart, dumb, train wreck, etc.
The ego boost the cheater gets is from someone who is willing to take seconds or worse yet, basically be used. They don’t "love" each other - it’s infatuation and being used to get some thrill or excitement in their life.
The more confident you get in yourself, the less other people will affect you. Honestly if my H openly flirted w/ someone in front of me, I would have no problem D him. Yup that’s where I am - zero tolerance and no second chances.
I’d like to say that since dday2 11 years ago, I am more confident and sure of myself than I ever was. I don’t care what other people think and my opinion is the only one that matters. My H either lives up to my expectations or not. His choice.
But if I am not happy, and he’s the cause of it, it’s up to me to do something about it. All this to say that if someone is friendly to your H, that’s okay as long as there are boundaries and he behaves appropriately.
My H no longer allows people to touch him — even my close friends who are NOT interested in him. He understands the disrespect he showed me and has adjusted his behavior accordingly. If your H has done the same, I think you can relax just a bit and not be so bothered by other people.
I also have protected myself in case he ever decided to kick me to the curb again. A post nup is a wonderful thing for my peace of mind.