Hmmm, ask her into the office to explain herself. Be straight and strong with her, make her understand that you wont stand for this sort of bullshit. If you don't like her attitude once you've given her this telling off, or she comes back with abuse, inform her that you're giving her an official verbal warning. Send her out to shop floor and make a note of everything which was said so that you can show your superior once they return.


Cheers,
Grant