Franky,
This is a good idea for an article itself. I think most guys need it. "What to do when women (stranger) start vilifying you". Chase, we need this.
But in the mean time, Here's some tips.
1)Don't be fazed by it. (even if you are at first, quickly get your act together)
2)See whether she's serious or not.
3)Just propose to leave and leave or fake a smile and leave.
After that, Check back on your game to see if you scared her or move way over the line.
Zac