I'm really so sorry that this happened. I will keep her and her baby in my prayers. There are many triggers to when DV starts. It's ownership. It could be when you are really close, or you move in together. A baby could signify that your are abandoning that person for the baby. It seems like this is what happened here, but don't want to speculate.
After feelings of ownership is feelings of abandonment. Whether real or not. My hope is that people here really do listen to things like this happening.
Other then that, just speechless......
((((((((((((((hugs))))))))))))), and wishing for a speedy recovery
amy