I hope it's OK that I'm chiming in. I read through your posts, and I'm really sorry that your trauma from abuse has been invalidated by your parents for so long. It's not your fault, you're not overreacting, and it's definitely not okay behaviour or "how kids learn to behave". To address something you said in one of your earlier posts: there is
a way to deal emotionally with what happened to you as a kid, and also to prevent it from taking over your life. It will definitely phase you though; it's meant to. And being phased by the trauma you suffered is a good thing, because that's you validating Past You's suffering, when your loved ones won't/can't. And that's the best thing anyone can do for themselves--for their past, present, and future selves.
It's inevitable that we internalize the reactions our loved ones have to our struggles, which is why you're walking on eggshells in your own brain. But I hope you can slowly accept that your brain is your own private healing space, and that you need to be there for yourself and your trauma right now when your parents won't. This article
may also help, let me know if it does.
I understand why you're cautious about talking to your issues with your friend Sara, but I'd just like to repeat what you said: trauma isn't a competition. Support and advice among friends has nothing to do with who's had it worse, as long as no one is invalidating what the other person went through. In fact, Sara might have some pretty insightful things to say about your situation, if she's been through similar stuff before. And by making yourself vulnerable in front of her and letting her in on what you've suffered, you may be helping her out by giving her space to reflect on her own trauma, with a friend who gets it. How does that sound?