I feel like there is some missing information here - what do you mean by BM was trying to "win".  And what do you mean by "tolerating her BS all these years"?  How has DH been handling this stuff from BM?

Sounds like BM has been bashing you to the kids for quite some time, and this was the tipping point that she used to competely alienate them from DH.  My SS was under a lot of pressure to hate DH from his mother, but he usually was well-behaved and happy at our home anyway.  But at a certain point, she was able to entirely alienate him and he no longer has much of a relationship with DH at all.

You made a mistake, but if DH divorces you over that, then he's a fool. He'd be giving BM and the kids so much power.

Very sorry.  IMHO, facebook should be limited to sharing with close friends and family.

Don't what you said or what she said, but if you called her a cheater on a public page, I can imagine that woudl not end well.  Also, IMHO, relying on what only one spouse said about a marriage or divorce is never a good idea.  

A "good" mother does more than cook dinner, laundry and drive them around. A "good" mother would not have shown a bunch of teenagers a message back and forth between you and her. The kids are being played here and your DH needs to show them that. I would suggest that even if it has to be enforced that all of you meet with a family counselor that specializes in blended families with toxic co parents. What BM did was a calculated attack on you and your DH. These kids aren't toddlers and should hear the truth about this manipulation in a controlled enviornment where the converstaions can stay on topic and on track. 

You might want to try counseling to head things off but go a couple of times by yourself first before bringing him in.  You would be shocked at how many counselors are very pro-first family even without BM and the kids as part of the process.  The last thing youu need is a counselor telling him to put them first on top of everything else!  Look, you took her open nastiness for years and no one cared.  But the minute you said anything to defend yourself you get crucified.  Obviously that is something a kid is going to feed into but if your husband does too then he is an idiot and you have every right to ask him why he even bothered to divorce BM.  

I'm sorry you got into this situation.  Unfortunately, it really can be a mess when we let ourselves stoop to their level.  I honestly don't understand how your husband is being blamed for things that YOU said... unless he was also getting into it with her.

Maybe it would be worth one more try to bury the hatchet with his EX and his daughters.. and it may require being the bigger person and accepting "all" the blame with your apology.

Dear BM,

I wanted to apologize for saying those things to you on facebook.  Not only were they unkind, but in all honesty, I have no basis to even know if some of those things were even true.  It wasn't my place to call you out and as the mother of my husband's children, I should have treated you with more respect.  When it comes down to it, I wasn't there when you were married to DH.. and I'm sure that no one was without blame for why it didn't work out.  But, what I do know is that you have raised two amazing daughters and from everything I can see, you are a great mom.  I really admire your parenting. 

Again, I'm sorry I said hurtful things to you.  It was wrong of me to do that and I hope that you can forgive my lapse in judgement. I'm embarassed because I should know better. I know we don't have to be good friends given our situation, but I hope at least we can be civil and cooperate to the extent that it benefits the kids.  Thank you for taking the time to read this.

W4Love

And.. yes,... I understand "she started it".. but ultimately, if the goal is to move things in the direction of reconcilliation with the kids.. this may be the bitter pill that needs to be swallowed.

I will say, that if the girl's relationship wiht their dad was so great.. I can't see how he isn't getting a chance to see them.. even if it means outside the home.

IMO you are going about this all wrong.  You obviously have one of "those BMs", one that won't let go, (as you posted) and finally found a way to cause strife.  

Your DH needs to take BM by the horns, call her out on her actions and put her and the skids on notice that you are his wife, he has moved on from BM and that there is nothing they can do to change it.  It is high time that they all respect his decision to marry you and to stay married to you.  

The skids are teenagers and the way they followed BM's lead so easily shows me that she has been laying this trap for the skids for years.  She is a most foul type of BM, full of evil and lying in wait for the right moment to strike.  

How nice this happened right before Christmas.  DH is the only one who can shut this down and he needs to either support his marriage and put his own happiness first (the adult thing to do) or his can follow BM and her games to be her eternal pupppet, allowing the skids and her to control him the rest of his life.  

Things will get worse before they ever get better but I bet if you take a hard look at the past 4 years, you will see how BM has been playing her long game to destroy your marriage.   Is she a good mom?  Is that in public?  She sounds like a master at impression management, she had an affair with DH's best friend and came out of that smelling like a rose????  Hmmmmm,   something isn't right about that.  

I'm going take a guess and say DH took the high road and hid BM's actions from the skids.  They are old enough for facts and truth but it has to come from him.  Not you.  

This is one hot mess and BM is sipping wine and smiling over her first victory.  DH needs to decide if its her only one or if he will allow her to win again.  THe skids are only bit players and weapons in her plan.  

So BM has been baiting you and DH for years, but because you lose patience and retaliate the one time,  it is now all your fault?  Sorry, that just doesn't wash with me, although it is very self serving for BM, the SKIDs, and, it appears, DH also.  They have all joined in and made you a scapegoat.  

I called BM a whore straight out in front of the skids once. Not one of my prouder moments but I won't lie and say I didn't. DH tried to get snippy with me about it in private and I shut that down. "Did she cheat on you multiple times?" "Yes." "Did she parade her side d*ck around the kids before you got divorced." "Yes." "So what I said was both true and something she's already shown the kids?" "Yes, but..." "But nothing. If you want to be mad at someone about this, be mad at your (ex)WIFE for cohosting SS's bday party with her side d*ck while you were out of town working."

The only thing you should be ashamed about, OP, is that you feuded with a b*tch on Facebook like a 12 year old. 

She baited you and you fell for it.  Not your best moment but you are human.  I am absolutely sure there is way more to this then you are aware of.  If she has been trying to get him back then she already had a plan up her sleeve.  She has done way more than show them a few crap talking texts.  She has probably told them that she cheated on their dad because he was having an affair with you or something.  I wouldnt put it past her and she can not be that great of a mom if she is ok with then not seeing the other side of their family.  It sucks hun but aside from counseling I am not sure what you should do,  What has your husband said. Is he blaming you? 

Don't be so hard on yourself. You're only human and after years of dealing with her bullsh!t I can see why it pushed you to act out of character. Forgive yourself, move on from it, and know this is a lesson learned. The lesson is not to engage with crazy because she will use it as leverage. She baited you and you bit. I wouldn't be surprised if this wasn't her intention from jump.

She used this as icing on the cake to use the kids as pawns and isolate them from you & H. Keep your chin up and know that this is in no way your fault. Its not your fault that your H had children with a toxic manipulative woman who uses her kids. Yes, you engaged but at the end of the day its not to punish you forever and be the end all of the kids having a relationship with their father.