Sounds like more of a test than trying to get rid of you or a retaliation to your neg.
When you say a neg you move on with what you're saying to the rest of the group. Don't give her a chance to think up a comeback or be ready for one if it comes.
She may have been testing you to see if you were just some other guy trying to pick her up by talking to her or not. Focusing more attention on the other girl would've helped but keep her entertained as well. I would've negged her again or said something witty and funny then move on to a dhv immediately.
Girl 1 "If you care so much, maybe you should go over there and save them.."
Fox: "I would but my superhero costume is at the dry cleaners
You know something got me thinking of this. Have you ever had a pet that just knew what you were thinking? (most people do) It's kinda like they can read their minds. Here let me try something with you guys really quick. Do you believe in ESP?"Pretty much just let it flow. Choose whatever you want and go with it. If she's still a bitch after you DHV with her friend feel free to eject or neg her again with something like:
"Is she always like this? How do you go anywhere with her?" etc etc
If she continues to be a bitch eject. I like to break her autopilot first though. Basically say what she's thinking. If you get it right she'll show it. If not eject anyway.