Hubby was at a dance, ex knew this and he sent pics after dance was over (completely a reasonable time frame), biomum is batshit angry because he didn't drop everything for her.

thats the game she plays, the more everyone entertains this, the more she amps up. She gives 1 hr notice to daddy about school dance and says well at least i gave you notice. Hypocritically if you go into labour and she is notified a month or several months/weeks before of likely due date and you notify her 1/2-1 day before that you are in hospital, you can be damn sure she'll lose it at how inconvenient and rude you all are and inconsiderate of her and what a bad daddy hubby is.

the moment you all stop responding to this, end the dropping everything for her and make it damn clear firm responses of "we were at the dance you gave 1 hrs notice to me of to plan and prep for our daughter so if it didn't go to plan, you could paint us as the baddies, you knew we were at the dance and likely busy so NO, I WILL NOT RESPOND SOONER. Any further communication from oyou of this sort will be ignored as they serve no other benefit than to create drama and arguments" and act on them. 
 

when she starts getting the silent treatment she will test you all, ignore, enjoy life, it will die down. Play her game better than she is playing it. These hc bio mums are all operating the same game. They're not very bright so play their game better. End her control, end her power over you.

i had 2 kids with my husband, when we were on the way to hospital, hubby told his son who was 17.5 & 19 when i delivered both kids, that we were on the way to hospital. Nothing he had was as urgent as what we were dealing with now. If ss tried to guilt hubby and make it like his stuff was urgent, hubby wouldn't tolerate it. His focus was on me and our kid(s).

you are giving this woman too much space in your head. It doesn't matter why she is such a witch, she just is. Ignore her. She doesn't need to contact you, so block her if you haven't already. Your DH needs to turn his phone off when he has his daughter on visitation. There is no reason for her mother to call him when it's on his time. I'm not very phone-savvy but is it possible to have all of her texts sent to a directory as soon as they arrive should she start bothering him during his time? That way he can either ignore them completely or read them at his leisure. 

I suggest you google "grey rock technique". 

Does your DH have a CO currently in place? If he does, he needs to follow it to a tee. If the CO grants BM x days of visitation and DH y days of visitation, you follow it, not a day more or less. If a super fun event happens that BM or DH wants SD to be involved in on the other person's time, too bad. If the CO grants either parent x number of phone calls per week, each parent only gets x number of calls; any additional calls will be ignored. It is unfortunate that you have to be that strict but if you give BM an inch, she will take a mile. 

Your DH needs to limit communication with BM. He needs to make an email account for BM communication only then he needs to tell BM that he will only communicate via email and provide her with the email address. If she continues to text, he either needs to ignore her or respond that he will only communicate via email. If BM inundates his email with tons of messages, he only responds to the relevant ones and he keeps it BIFF - you can Google it. He is to only communicate about the child. If BM emails about SD and then goes on a tangent about how horrible DH is or how much she hates you, he only acknowledges the part about SD, ignoring the rest. All responses shouldn't be more than two to three sentences in length. If BM set SD's phone to "auto-answer" then the phone is turned off and given to DH for the duration of the visit - SD can call BM via house phone or DH's phone. 

Your DH also cannot continue dropping everything for SD. If BM provides little to no notice, DH doesn't go. If BM then blows up his phone because he didn't go, he ignores it. BM can portray the deadbeat Dad mantra all day long, but if she is high conflict, she is going to do it anyway whether he shows up or not. BM needs to learn that DH won't come running when she snaps her fingers. 

You should not be doing transportation, period. If DH cannot do the transportation, then SD doesn't come or the times need to be changed to a time that DH can do it. By sending third parties, he is opening those people (you included) up to possible allegations. BM could claim that you beat her up during an exchange and it would be her word against yours. If DH is doing transport, then he needs to record every pick up and drop off to protect himself from allegations (research state laws to determine if one party recording is legal in your state). 

Finally, if SD continues down this path of parental alienation, she is also a threat to you. She could accuse you of God knows what, putting you and your kids at risk. If SD accuses you of abuse and BM runs with it, you could face a CPS investigation and possibly lose your own kids. I would take caution around SD and if she continues, ask DH to see her away from the home. You can't prevent PAS and there is nothing you could have done previously to have "improved" the relationship. If BM wants to PAS, she will do it. If you try to counteract it 9 times, BM will push back 10 times. At the end of the day, SD will either PAS or she won't, but that will be on SD and her loyalty ties to BM. 

This situation only gets easier with strong boundaries. It doesn't make you guys bad coparents because BM was never able to coparent from the start. You guys are just doing the best you can to protect yourselves and your kids. Once BM realizes that she can't break down the boundaries, she will slow down and all of this drama will be reduced.

I speak from experience - it has taken 7 years for our drama to die down, but we are finally at a decent place where BM only ramps up a few times per year. It used to be every single day, multiple times per day. Hugs to you! 

They get no support or consideration.  The more toxic they get, the more they are confronted.  

The key is to keep a rolled up copy of the CO handy and beat the snot out of them, figuratively of course,  with it in court each and every time they get obtuse.  

Lather, rinse, repeat.

Zero tolerance is the tool for keeping toxic dipshits under the slime covered rock at the bottom of their shallow and polluted gene pool where they belong.

IMHO and contrary to common emotional belief, kids need to see a toxic parent put in their place.  This is far healthier for them than eternally watching that toxic parent be toxic while the other parent shows no spine, courage, or balls in keeping their boot on the throat of the toxic parent. Again... figuratively.

smh

You are not the parent. You don't have any responsibility to drive this kid around, pick them up, buy them anything, or do anything other than be civil while they are in your company. Tell your husband to stand up to his wife, or this will only get worse. Its time for you to disengage from all parenting activity and let DH do his part. I think you will find this is a HUGE relief. 

Write it out here. Are you in therapy for dealing with your childhood dealing with your toxic mother? I would suggest that, as what you mentioned you were triggered, and are having anxiety.

BM is very disordered. And is triggering you. Taking the emotion out of it will allow you to think clearly and strategise.

Parental alienation is starting to be recognized. When it happens its miserable. After they grow up and age out, they either try to use the alienated parent, punish them, or are estranged.

I wish there were a simple solution. Therapy and educating yourselves. Its really like doing battle.