I'm afraid you can't really force her to do anything. It's not a legal issue and she once was "Mrs. YourLastName."

I once was Ms. MaidenName, Mrs. FirstHusbandLastName, Mrs. SecondHusbandLastName and I'm now Ms. MyNewLastName.

Even though I legally changed my name in 2020, I have signed documents with SecondHusbandLastName because it was once my last name and the thing I was signing didn't have any legal impact.

She wants you to be upset. Don't give her the satisfaction. She COULD have legally kept his last name because her kids likely have that name.

I know it's hard, but don't let it ruin your day. Just enjoy the fact that she's clearly obsessed with your happy life.

I agree, completely, with la_dulce_vida. Because your DH dared to file for contempt and was successful, BM is probably burning with quiet rage. Rest assured that she'll engage in any retaliation, no matter how minuscule, in order to let you both know that she still wields some power.

The most prudent course of action is to ignore her nonsense; if she discovers that you and DH are disturbed enough to reprove her, you’ll be playing right into her hands. The best way to deal with minor aggravations from HCBMs is to ignore them. That’ll frustrate her more than anything else you could do. Again, as la_dulce_vida has written, there is no legal avenue available to stop her from using your husband’s surname.

So, Hon, don’t let it bug you!

She's probably feeling insecure because you have the same last name as the kids but she doesn't. Makes me wonder if she's been a neglectful parent and therefore her insecurity is warranted. Whether it is or isn't, not much you can do about it.

I actually never changed my last name after my divorce 13 years ago. I had recently graduated school, had a new professional license, and a job where people scheduled appointments with me. It seemed too disruptive to change my name less than a year into trying to establish myself. If i remarry, i will take my husband's name. But for now, i have zero ties to my ex. Kids are both over 18 and the youngest, who is still in HS, lives with me full-time. Ex doesn't pay for anything and we don't talk. 

This comes under "pick your battles." I would let it go. It is strange, but there is nothing you can do to make her stop. Everyone else thinks it strange as well, so you know you are not the only one. If DH confronts her, it will just cause issues and it is not worth it.

If she petitioned for the return of her maiden name and surrendered your DH's last name, she has no right to use it.

I would have you attorney send her a cease and decist order and if she does not comply, consider filing fraud charges.

My XW thankfully surrendered my name at our final divorce hearing. She got nasty about it, the Judge spanked her pretty hard about being nasty.  I was relieved that my name would no longer be polluted by any association with her adulterous serially cheating self.  I blessedly avoided polluting my gene pool with her.

She has the right to used her maiden name. But doesn't have to.  In most cases when she if she remarry, she will remarry in maiden name. As marry name in Jones. at weddings the parents if SMITH invites to a wedding. Most men don't want to married a woman using her exs name

There is nothing you can do, most places will call her Mrs kids last name .   This is common, just one of the enjoyment of S.life.  The man who married her will have a life time of being called Mr. Ex last name because so many thing is in her married namev

If she's engaged with a baby 

• she's not married to her fiance
• shes probably going through something ... mentally 

I know if I had a baby with my fiancé I would be using my fiancées last name (unless I was embarrassed by him - in that case why would I have a baby with him - or embarrassed to be "unwed" in a conservative area) ... "look James I think you forgot the marriage license before this baby got here so I'm going down to the clerks office and having BOTH me and our kids' last names changed with or without this marriage license so we can present as a family unit now which do you prefer?"

When kids have different last names than their parents it becomes super obvious of "single mom" (women have this stigma more than men) and she is probably embarrassed to be viewed a single mom (or have her kids be judged harshly at school) if she's in a conservative area hence why she's keeping her last name at school so no one know the kids aren't in a nuclear family household. 

I personally wouldn't say anything to her about it bc that's going to probably make her want to sashay around portraying her charade as reality even more. 
 

I would make corrections if necessary when people seem confused "yes I'm Mrs Jones ... Bob's WIFE ... so let me know if there is anything you need to assist little Timmy at school" 

It's a control thing. BM did this. She was remarried with her husband last name and I randomly got an email from SDs teacher and it was to me and BM. BM responded with SOs last name... funny thing her email had her remarried name..

Like ok who are you today?? She did that as a push over to me IMO.

This type of behavior is petty and the teachers will see thru her craziness. 

I'll add (just for background) my skids 20,19, 16 stopped going to her house completely almost 6 years ago. That's why in my situation it was 100% a jab at me to use SOs last name.

Not going to lie.. I REALLY wanted to forward that to her husband (who got his wish of a child free life) and let him know his wife was using her old married name LOL. 

DW did not have much issue with schools calling her by the Spermidiot's last name. It was nearly a never happened thing.  Oddly, the assumptions of the schools always seemed to be that she was SM married to BioDad though SS did not have my/our family name until he asked me to adopt him when he was 22yo.