A while back Simple Justice put up a post giving his answer to whether someone who harms another in self defense has a duty to render aid.
I don't think the answer to this is all that hard. No, you're an idiot if you put yourself within arm's reach of someone who has tried to do you serious bodily harm. The extent of your duty is to call 911 and tell the police where the injured person is.
The right to self defense kicks in when someone is trying to harm or kill you or others. HARM OR KILL. You never place yourself within striking distance of someone who has done this. The fact that she appears injured, even grievously, does not mean that she can no longer harm or kill you. She could be faking; she could be hopped enough on drugs or adrenaline and still be able to harm you; she could have a gun or knife you don't know about. Specifically, if you are defending others you have a duty to remove them from the potential for harm. You cannot guarantee their safety by remaining at the scene.
On the other hand, it is your choice if you want to go above and beyond. You have no duty to render aid (other than calling and reporting), but the choice to remove yourself from potential harm is yours to make. If you choose to go above and beyond and expose yourself to the continuing potential for harm that's not a duty, that's saintly behavior.