Here is the advice from my friend, who runs the shelter for battered women in our county:
I hope this helps.This is always so hard; because the person we have to defer to, ALWAYS, is the person who is being abused. And until they are ready to say "Enough", it will not stop. She has to make the decision to change and from what you are saying that's not happened yet. And yes fear plays a huge factor in this. Abusers are usually very good at controlling the situation so that she stays; usually out of fear; but not necessarily out of fear of physical abuse. In her case the abuse is bad and getting worse; if she doesn't do something soon; he most likely will kill her. The fact that she is pregnant is scarier still. If he decides it's time to beat her up and she's still pregnant it won't stop him. Abuse is about power and control; not love. But people who are in relationship do not see that what they are experiencing is not love; probably because the abuser uses the term to gain control. "I love you so much; I wish you wouldn't make me hurt you." Yes that's been said over and over again so it's hard to judge what is, and is not, real in an abusive relationship.
The best thing that you can do is to educate yourself about what you can and cannot do in your state. I do not know the laws in the state of Washington. Our friend has already advised you to contact the local women's shelter and to talk to the police; that's the best thing you can do. Knowing what is possible is the best tool you can have. Learn about the "power and control" wheel, the cyclical nature of abuse which is NOT a circle but a spiral, will almost always get worse. Find options for her and let her know what they are if you can because the next best thing is to be supportive of her when he can. A caution I would make is that because you can be seen as a rival for her attentions from her abuser is that you be very circumspect when dealing with her.
This problem is not easily solved and there are ramifications for almost every action she can possibly take. Please be mindful of what you might encourage her to do. Because control is the issue here and not love; if he were to lose control he would then have to get it back and it can get even uglier than it already is; up to and including death. Again educate yourself first. There are many websites that can help and or inform.
http://www.ncadv.org/files/DomesticViolenceFactSheet(National).pdf
http://www.athealth.com/Consumer/disorders/DomViolFacts.html
This website is based in Indiana but it's got good information:
http://www.clarkprosecutor.org/html/domviol/plan.htm this one talks about a safety plan; THAT is SO important. This is a piece to give her no matter what. I don't care if you put it on her desk anonymously; she needs to see it. But look it over first as it's based in Indiana; see if you can get one from the local women's shelter for her.
http://www.clarkprosecutor.org/html/domviol/domvic.htm
This site is based in your state: find the Shelter closest to you.
http://www.wscadv.org/gethelpnow.cfm
This one is a list but read the previous one; it has lots of information.
http://www.sboard.org/SHELTERS/WA.HTM
This is a big nightmare for her; one that she cannot get out of without first making a huge decision and it's only going to get worse; the baby will not help the situation at all. That I know.
I wish you patience; and I wish her peace.
PS: I've really only scratched the surface of this; please talk to someone in your state; it's so important.