it all seems far to soon and especially for my daughter - I don’t know what to do to protect my daughter.
Sadly, there isn’t much you can do at all as he has well and truly moved on with little regard for DD’s feelings.
It’s a very difficult situation for you as you don’t know if he will abandon her entirely or suddenly want 50/50 access, so you have to be prepared for both eventualities which is almost impossible to do.
You don’t say how old DD is - it would be easier to help you if you could tell us. Hopefully she is in secondary school and old enough to decide some things for herself.
You will already be giving your daughter as much extra love and reassurance as possible now her dad has moved out, as no doubt she already feels totally abandoned by him. This new baby development will have added to that feeling. And she will have lots of feelings confusing her and making her anxious, depending on her age. Anger, insecurity, feelings of rejection, missing him, blaming you etc etc. Be prepared for all that. Demonstrating your own strength to her will help lead her with confidence through this awful stage …again depending on her age.
If you could afford to find some extra private therapy for her to help navigate that confusion it might help. Or maybe a special relative or friend could also take an interest in her to help guide her through it and help make her feel more secure. Giving her somebody extra to talk to other than her mum would be good.
It might be good to inform her school too and find out of there might be extra support available there. If she is close to his parents, then hopefully, they can still see her and continue to make her feel special and loved.
Be very aware of parental alienation down the line OP. It won’t help DD at all to ever hear you speak badly of her dad and hard as it is for you, the new baby is a half sibling she might want to get to know. Validate her feelings and reassure her that although her dad is a bit pre-occupied for now, he does love her.
Having moved away, her dad might find it difficult to see her as often as he should especially when he has his hands full with sleepless nights, but if his new relationship lasts he may suddenly decide to try for more access. It will be easier to support her once he reveals his situation and intentions more fully.
You have had a shock OP and I hope you are ok. It is so very hurtful when this happens and your ex suddenly expects DD to be part of a blended extra new family as if it’s entirely normal. Don’t forget support for yourself too. Take care x