Over here in the States, grandparents do have rights situation dependent.

The fact that she stopped meds during the pregnancy could be something her doctor was aware of?

Do you have women's shelters or hotlines over there, even just to call and ask.

Domestic violence is such a tough scenario when the victim is in denial and trying to protect the abuser.

What can your bf do to entice her to stay for a while? Uplift her and encourage her there is a better life away from this person whom she probably feels at this stage is her only supporter. Keep in mind the mental warfare she's probably been through to reach this point.

Hopefully others know resources and how things work over where you are.