Sending you a hand hold, OP. I'm in the same boat, playing out in real time. I've been dealing with the repercussions of what my DF has done for almost 2 years and I can tell you it's hard. But you know that already. DM still alive and won't change her will even though she's at high risk of decisions being made that put her best interests behind doing what's best to realise the gifted asset in the will.
Situation very similar. Sibling - in my case, an entitled sister - manipulated parents into leaving their house solely to her. She orchestrated a massive falling out with me so she doesn't have to face up to the fact she's been a greedy, entitled cunt. I've been the more successful child, she's a financial car crash and narrowly avoided being repossessed after having almost £200k in equity that was frittered away. She walked away with nothing and now rents. New narrative is that "she needs to buy the house she's in."
I think people who haven't experienced inequality from parents particularly after death, don't understand the feelings it gives rise to. It's like an affair, actually. The betrayal is similar. Like Emma Thompson's character says in Love, Actually "you've made the life I live foolish too", You've been bowling along thinking things are one way, when actually they've been completely different. Hurt like that is very difficult to get over.
What makes me most sad is that it has tainted all my memories of my parents. I was due to receive my dad's watch, which had been his dad's. I have wanted this watch as a keepsake for so long, and now I just don't care for it anymore. I don't want anything. Is this childish? Perhaps. But it's how I feel. I just do not want anything at all. The hurt is too great . When I saw my dad's signature on his will, signed feebly just 2 weeks before he died, so pretty much the last thing he did I just wanted to cry. It was like being punched in the stomach.
But the thing is, OP, it's done. And you're wasting valuable time in your own life by not being able to get over it. Don't let them have any more of your time. Hold your head high, know that you are not capable of this sort of behaviour yourself. Forgive yourself for some of the vitriolic feelings you have and be kind to yourself. You did nothing wrong. We can't help the families we're born into.