Facebook is a tricky thing to navigate. If all the things you say about her a true that's really sad. I feel bad for her child.

However, you did say hurtful things and outed her on Facebook. You basically told the entire world about her dirty laundry. If someone did that to you it would hurt really bad even if you were totally in the wrong.

Frequently in dysfunctional families the person who stands up, opens their mouth and says "hey, we have huge problems here" is labeled the bad guy. I've been the evil daughter for thirty years because I said my mother was an alcoholic. She was and still is.

I think your mistake was doing it on Facebook. It's not anonymous like here on the forum. Don't beat yourself up about it. You screwed up you've learned from the experience. It's probably a good thing that you're blocked so you won't be tempted to go back and repeat your mistake in a moment of anger.