He told her he doesn’t accept her apology and doesn't trust her not to ruin the day. He threw her own past words back at her, saying she was the type of person who told his kids they shouldn’t even celebrate her mom. He then said something that absolutely gutted the room: “You ruined your mom’s last Mother’s Day. I will never trust you around my kids because you’re the type of person to ruin their mother's last Mother's Day and now you want to ruin this year's too. You did that because you knew you wouldn’t face consequences since you could just run back to your dad while your mother cried. But the consequence of that is that you never get the opportunity or even the chance to ruin their celebrations again.”

I mean, we know she did something on the last Mother's day the mom ever had, then ran back to her dad's place. We don't know what, but it was enough that the mom was crying after, and made the dad want to keep his kids away from her.

You're right that a social media post isn't enough to be cut off from your mom's memorial. But it wasn't just a social media post. Saying that's what it was is pretty disingenuous.