Hi Dee,
My heart goes out to you and your daughter in this difficult situation. As a mother it is heart breaking to see your daughter going through this hell whilst you feel like a helpless bystander.
I myself was in a physically and verbally abusive relationship and from experience there was not much anyone could say that would make me leave the man. It took years of abuse and finally a rude awakening that I was better off without him. Unfortuntately, it doesn't come without scars and any abused woman can tell you this.
An abused person knows in their heart that what their partner is doing is not right but abusive partners have a wicked way of controlling, of manipulating and making you feel worthless. They do this in a number of ways such as withholding their love etc. constantly undermining you etc It sounds to me like your daughter is still hanging on to some kind of hope because otherwise she would not still be staying there especially after you have offered to assist her. My ex tried the same with my mother, he did and said all he could to turn her against me with the most wicked lies until she nearly had a break down. He would even phone her after we were seperated and getting a divorce. He wanted to see my life a perpetual hell. People can be so wicked.
She definitely sounds depressed and this is not good for her or the baby. Depressed people go into a spiral of hopelessness and see no way out. I don't know what to advise. Perhaps some councelling \ therapy as was suggested. My thoughts are with you. There is no quick solution here. I can see you are there for your daughter, don't ever give up on her.
Visit my blog if you want to read more on my experiences
http://blogs.women24.com/Hope_Full