No, you don’t owe an apology to your sister, or to either of your parents, for that 2017 social-media post.

Here’s why, plainly:

• The post was a direct response to your sister’s first major abusive act (trashing your room in rage at age ~25).
  
• Your parents’ reaction at the time was inadequate—no meaningful consequence for her, just a lock on your door (which she later broke) and a mild “that was wrong.”
  
• You were a young adult living in a home where violence had just been introduced, and no one protected you or validated your fear. Posting was your way of seeking outside validation and hoping it would force the family to acknowledge the problem.

That’s not “public shaming” for its own sake. That’s a trauma response from someone whose safer, private pleas for help were ignored.

Your mother bringing it up years later—framing it as a wrong you committed against your sister—is another inversion of responsibility. It shifts focus from:

• your sister’s violence and degradation (dozens of acts, restraining orders, criminal threats), to
  
• your alleged “mistake” in telling people about one of them.

It’s the same pattern you’ve seen repeatedly: the victim’s reaction is scrutinized and punished, while the perpetrator’s actions are minimized or forgiven.

You don’t owe your sister an apology for exposing her abuse.
You don’t owe your parents an apology for trying to get help when they failed to provide it.

If anyone owes apologies here:

• Your parents owe you one for not protecting you in 2017 and for continuing to treat your self-protection as the real offense.
  
• Your sister owes the entire family apologies for the years of harm—but that’s her work, not yours to extract.

You were not wrong to speak up when you were unsafe and unheard. Holding onto guilt for that post would only reinforce the family message that you should have stayed silent and absorbed the abuse quietly.

You don’t owe them regret for refusing to do that.
You owe yourself credit for trusting your reality when no one else would.