If you break into a house with friends and your friends get killed by the homeowner you get charged with murder. It's the same concept. If you start violence with a baby in your arms or uterus you deserve to face consequences if you started the violence. I mean I witnessed this shit irl recently. If I have a baby in my possession I have two modes in which I'd deal with threats, absolute peacemaker and instant kill/takedown. Side note, I'm not flexing, I'd just do what I could and those would be my goals, who knows if it'd go in my favor. This woman, if she started the violence, deserved the charge, unless the other woman said I'm going to kill you or hit you. If she was threatened with physical violence I couldn't blame her for attacking because it could hurt the baby or her.
Anyways tl:dr Whoever started the violence deserves the charge, unless the other was threatening life or limb.