It doesn't mean it was all fake just because she said some things on the internet that were unfair or untrue or too personal.
I agree with Puffin, you don't know what you have done yet.
I've been on the receiving end of lies within the family as part of issues my MIL has. She is a manipulative and spiteful woman who never misses a chance to make a hurtful comment or play the victim. She has made some terrible comments about the two of our children who died as babies and behave incredibly badly the evening before our sons funeral, causing a massive amount of upset.
Then, because our relationship was strained because of her behaviour she made it her mission in life to let the rest of the family know just what I am really like. She's used those words, much the same as you have here. She and FIL have done their best to convince DH that he doesn't really know me, even after eleven years together, and tried to split us up. They've told me they wished DH had never met me.
It's not the same as your issue but the end result has been devastating. I no longer see or speak to PILs, DH rarely sees them and they haven't seen our son for a year now. DH and his eldest brother are no longer speaking because BIL took PIL's side and started a harassment campaign against me that involved late night abusive telephone calls and ranting text messages calling me names and accusing me of lying about everything.
DH's other brother hasn't spoken to me in months, deleted me from Facebook to make the point that he is siding with his mother and refuses to see us unless we meet him at PILs house. Meaning our DS hasn't seen his cousins in a year either. They are emigrating soon, so he probably won't ever see them now. DH is prepared to never see either brother again because he thinks they are wrong to treat me badly. SIL is torn and doing her best to keep her relationship with everyone as amicable as possible but whenever we meet up there are strained moments when she almost mentions her parents and then doesn't.
All because MIL couldn't accept that she had been wrong and wanted everyone to take her side and realise what I was really like. I don't think even MIL expected this level of destruction to spread through the family, she's the sort that is casually cruel and then surprised to see people are upset. She disowned DH last year, said they were finished with him for good and then wondered why he took her at her word.
It's not the same situation OP, I'm only telling you this to try and help you see how the entire family can be slowly eroded by someone's desire to show someone as they really are (in their opinion only). You have done more damage to the entire family than you will realise right now. This strain between your DP and SIL is going to spread like poison and although she made the mixture it was you that gave everyone the dose. It will harm your DP's relationship with his brother, it really will. I've seen it with my own DH and his brothers.
And all for nothing. Nobody has gained anything from this and I think there will come a day when your entire family wishes you had stayed off that forum or kept quiet about what you saw there. Including your own DP more than likely.