What can I tell them?
It sounds like your parents are having a hard time emphathizing with you. From the comments bellow the question it sounds like you may have already done the following but if you havn't then you should now,
Tell them the exact reprucussions you are going through.
Tell them about your nightmares, Tell them about the insomnia.
Make sure you tell them these things to your parents in private, you don't want interuptions from other people to derail the conversation.
Be warned your parents are likely to respond with something along the lines of
"if you would just forgive all that stuff would go away."
I hope your parents don't say that to you but if they do, it will be important for you to remember that they don't understand your pain. If they did they woundn't be pushing you to gloss things over.
So respond to them with something like this.
"How I feel is a direct result of my sister knowingly betraying me,
and insulting my worth as a human being by telling be that I'm a
Can you honestly tell me that if she had done this to you that you wouldn't
not feel exactly as I do?
You may want to consider doing the above in writing so as to avoid an argument. If you do tell them in a letter make sure to tell them that you are cominicating via letter becuase you love them and want to avoid a fight. The "love them" part is important because it precludes the claim that you wrote the letter out of cowardice.
If showing them the full extent of your pain does not diminish the preasure they are putting on you to reconcile, well, you will either have to keep repeating yourself, or stop seeing them as much.
"How do I respond when they try to get me to go to family events with
Tell them "I simply will not hang around some one who deliberately betrays me. I don't want to get close enough to her for her to betray me again, and it's too painful for me.
Do I just have to accept they will view me as the bad guy for not
accepting her "compromise" of sweeping it under the rug?
Probably. Unfortunately many people seem to lack the ability to tell the difference between some one who repents of something did wrong and some one who just want to gloss over their mistakes and pretend they didn't happen. Which is a shame because when you paint over rusted metal, it starts to flake off awfully quickly.
Were you don't follow your families religion It will be tempting for them to use the narrative that you are the black sheep of the family and your "lack of forgiveness" is just one more of your supposed shortcomings.
You can counteract this narrative by making extra efforts to show your family that you do care about them. visit them more then you normally would (when your sister is not there). Send them little letters thanking them for something recent that they said or did that was nice. If there is nothing recent thank them for something from a long time past. Call them just to say hi and see what's going on in their lives.
Side note if they try to talk about you and your siste say "I don't want to talk about it" and then ask them about work, your cousin, the dog whatever (to distract them) if they persist, Tell them kindly that you will end the call if they insist on talking about it.
By proactively seeking connection with the rest of your family you will over time (probably years) show them that you are a loving caring person, who won't betray or abandon them. And their narrative will slowly change.
In this portion I've included some response to all of the tactics your family uses to pressure you into forgiving your sister, or at least the ones you listed in your question. Please be aware that these responses are not designed to calm tensions. They are designed to set your accusers on their heals so to speak. To show the fallacies and short comings of their arguments. I include them because I believe it is important for us to be able to stand up for themselves. Don't just use these responses verbatim. They will be most useful to you if you think about them and write down how you feel about both the accusation against you and the response provided bellow. Writing down how you feel about the accusation and response will help you understand yourself, and the situation better. Which will in turn strengthen your ability to defend yourself.
It makes your mother so sad to think of her family never having a big
happy get-together again
Don't you think it hurts me too? My sister betrayed me, how do you think I feel?
You're being selfish, your sister's choice made her happy, don't you
want her to be happy?
That road goes both ways isn't my sister supposed to want me to be happy as well?
Well, I can see why what she did hurt you, but you shouldn't have done
XYZ in the first place
Two wrongs don't make a right, they just make more wrong.
Just because I made mistakes doesn't excuse her for betraying me, and telling me that I'm a horrible person.
It's been months/years, this is how things are now, you need to accept
How does accepting the situation help me heal my pain? I know that this is how things are now, That makes the pain worse not better.
She's reached out with those texts and you're not even giving her a
chance, so the rift is really your fault now.
She's not mending anything, what she's doing is pretending that she never did anything wrong. If the rift between us is ever going to be mended she must give me and honest heartfelt apology. Until she does our relationship can not heal.
But she's your only sister, you don't want to end up like [estranged
extended family member], do you?
No I don't. I also don't want to associate with some one who is willing to betray her own sister. I want to avoid being hurt by her again.
It must be exhausting holding on to all that anger for so long, I
can't even imagine..
Ya, it sucks, but you know, your passive aggressive comments only make the pain worse.
I'm glad your getting professional help. I'm not a psychologist, or a counselor, but I have seen first hand the trauma cause by personal betrayals. And it is indeed traumatic. I'm so sorry you have to go through this.
I've learned some things about forgiveness that it may be worth thinking about.
From your question, and my experience with this sort of trauma I'm going to guess that talking about forgiveness is frustrating to you. So if you find any thing I say below frustrating please feel free to call me an A** hole and quite reading.
1) People talk about Forgiveness as if you can just say "ok I forgive you" and poof everything is magically better. That is not how forgiveness works at all. Especially when betrayed by a close loved one. After all the lowest level of Hell is reserved for traitors right? (paraphrased from Dante's Inferno or Pirates of the Caribbean)
2) It's a lot easier to forgive someone when they are actually sorry for what they've done. Forgiving some one who's not sorry is somewhat a kin to grabbing a red hot rod of metal. your probably going to let go after 1/10 of a second because it's just too d**n painful.
3) Forgivness for this sort of hurt usually takes years. Also, you can forgive some one and still not trust them.
4) forgiveness is not about making the other persons life better. It's about making our life better. It's about escaping all the anger, and then healing from the pain (the anger is often a way of coping with the pain)
Good luck working all this out.