So my SO and I generally do not respond to BM unless it is 100% necessary.  She refuses to text unless it is an emergency and we can only email, except when she really wants to and sends a text.  She is super bitter after court where she did not get more money.  As an example of the communication...

She was denied an upward deviation for sports fees in court.  She emailed my SO asking for more money for sports.  She then had SD12 text her dad asking him to pay.  He did not respond and told SD12 they could have that discussion in person. So she wrote SO an email telling him he disgusts her and clearly does not have the best interests of the children in mind.  She told him our house is dysfunctional and some other adjectives I can't remember.  She told him she will protect the children with her life.  All of this because he won't give her extra money.

This is pretty typical. The communication from her swings from acceptable to abusive at some points within the same day.  So we don't respond as much as possible. We also generally don't point out things she is doing that are counter to the order if they aren't a big deal because she just goes off and it's not worth it.  

Today my SO went to pick up the kids at the time designated by the court order.  He got there and SD12 was not home.  SO text BM - given this was an emergency that a kid is missing.  BM responds she is at her friends whose dad will drop her off at BMs house.  No time given.

Ok so that's super annoying and very disrespectful. Not to mention counter to the court order.  SO doesn't want to say anything to BM as he thinks it will do no good.  I think he should so there is documentation of what she did and that he was not aware or in agreement.  Also so she does not continue to do this.  

What do you think? Is it worth saying anything?