Disengage. If your DH only had Sunday visits, then I can sorta understand why she'd be salty about that, and salty that she gets to spend one day a week with Dad but your kids get to be with him all the time. I can also see why she is jealous of the new baby, especially since she's a girl.

Now, understanding the reasons doesn't excuse them. You can disengage from her and keep your daughter (to an extent) and sons from her. With only one day a week, your DH can visit her outside the home. He can stay with family or just take her out for the day. Once she started lying, it becane dangerous for her to be around.

If your DH wants to call her, he can call her. Wants to take her out to eat? Okay. Movie? Sure. You don't need to be around it, and you don't need to police the relationship either. 

Who cares? What matters is she doesnt come around anymore, i would kiss the BMs feet if they kept their children away, trust me....Let the dad send money every month and give her a couple of phone calls....she doesnt like him anyway or else she wouldnt be talking shit about him and his child to her beloved BM

Leave it alone....focus on you and your children, thats what matters in life!! Hopefully BM keeps her daughter until she turns 18 or even older and dad can just meet her once a week in a local coffee shop or park lol i wish u the best....how i would love to be in your shoes with no antagonising children with ugly attitude coming over every other weekend....alas....im not

I only got "bitter" from your story. She doesn't sound sweet at all! Don't feel guilty about this. If you know you are acting in a fair way, stand your ground. 

Disengage, stay out of it, and let DH choose the type of relationship he wants to have with his daughter.

I went through hell with OSD and learned a lot from that experience as it almost broke SO and I up. I have used what I learned with YSD when she started the same behavior. 

I never did anything to damage SOs relationship with OSD. But I became the scapegoat. All it took was me simply pointing out OSDs behavior for him to decide it must be my fault because I don't like his daughter. 

No matter what sometimes parents will do anything to hold onto a relationship with their kids even if deep down they know the truth.

Even now that OSD has been kicked out of all her friends and families homes because of the same exact behavior. SO was pouting yesterday because I won't let OSD back into my home because he believes that is  the reason she is angry with him now. He then went on to say how YSD is upset she has to leave.

I stood my ground and told him that he is going to live with both his kids and will have all the time in the world to work in their relationship. I read him hateful messages sent to me from his kids. He is Thier father and I am not doing anything to keep him from having a relationship with them.  Matter of fact I am stepping aside so he can focus on have a relationship with them. 

But we all know sometimes if you give people what they want, they realize that's not what they really want. SKs say I am the reason they hate Thier father, SO feels guilty about it. Problem solved. 

I am not going to be the scapegoat, undervaiued, unappreciated, abused person. I know damn well my value, I know damn well what I have done for all of them. But some people can't appreciate something until it's gone.

I am taking back control of my life and from this point forward if they want a relationship with me it will be on my terms.

Just reading your blog and the comments it just makes my stomach turn, my blood boil. Dang I hope these SD's get hit by the Karma bus, the bus reverses and runs over them again. All these relationships and peoples happiness get spit on by these malicious b*tches. 

To the Ahole DH's who actually defend those b*tches, hell they are worse than the DD's. 

Step families are not for the faint of heart.