Advice please!!!

I'm going to try to keep this short. I need advice on getting a restraining order in Washington state. I don't know anything at all so any and all advice is very much appreciated. I have recently become pregnant with my boyfriend. He has another child with a woman who hates me for no reason. I've never been anything but respectful to her, she has nothing on me. Earlier this year when we told her we were pregnant she flipped saying she was going to kill our unborn child. I was going to get a restraining order then but the stress caused a miscarriage and it was not a huge worry for me. That was April and the threats have not stopped. Although that was the only one she texted to me she has continued to post threats on social media saying she's going to fight me. She never follows through and I'm really not scared of her at all. However now that I'm pregnant again I am scared for my child and I want to get ahead of things and get a restraining order before she finds out I'm pregnant. She is already blocked on everything. I have many screenshot of her posting on Facebook and twitter that she is going to fight me. She also recently got suspended from twitter for threatening another pregnant woman. Please any help on how I go about this. If I need a lawyer. How much it will cost. Anything! Thank you!!