Has she considered putting this baby up for adoption to a two parent, loving couple who is praying for a baby?
The most impressive Christians I know are those that accept the imperfections of others and demonstrate love in action.
Don't press your daughter to marry the co-worker, certainly not in the name of religion ... I don't think any branch of Christianity insists people who do not love each other (and one of whom is abusive to the other and possibly has psychological issues) should get married, whether or not there is a baby coming.
Do what you can to help her as she makes decisions about her future and that of the baby. Don't judge her, don't let others from the church make her feel horrible if you can stop them. Be there for her, tell her it that she is still your beloved daughter, and you have faith that she will be able to manage the situation effectively.
Well, she is an adult. She really needs to make her own decisions on this. I know it has to be very hard for you as clearly this goes against your own moral values. I truly respect that. However, she is an adult, and in my opinion, the best thing you can do is allow her to make her own decisions and be there to support her in the best way you can. This does not mean you have to agree with her decisions - but do try to be supportive. The last thing I am sure you want is for your relationship with her to be damaged. She is still your daughter, and this is your grandchild she is carrying. Attempting to force her to marry a man she does not love, and feels she cannot have a loving and stable relationship with is just a very bad idea.
Single parenthood is always preferable to an unstable two parent household. Your daughter does need to understand that if she chooses to have this baby, it is likely this man will now be a part of her life as the father of her child, and it would serve her and her child well to attempt a cordial co parenting relationship. But she really should not marry him only because there is a child. Those types of situations sadly rarely end well. I hope you will choose to be there for her and support her emotionally even if her choice goes against your own beliefs. She needs you right now. It sounds like perhaps some counseling might be a good thing for her too. I wish you all the best.
Perhaps she will get used to the idea once the baby is moving and she feel it, which will be soon.I dont think she should stay with the bf unless she wants to , if she didnt want to keep the baby ,there are many good people looking to adopt children ..good luck how exciting to be a gran