[Fizzyology]

I agree with Fey but at the same time I think you should take matters into your own hands as well. It's one thing if she's rude to her fellow employees but if she's being unprofessional towards her customers I personally don't think she deserves to have a job unless she can get her act together. If this job was important to her one would think she'd be kind to the customers.

If she keeps pulling these unprofessional and childish stunts towards you and the customers, talk to a manager. Explain how you don't appreciate how she's acting and that she isn't properly doing her job when she insults customers.

Honestly that's the worst and dumbest thing an employee can do and is certainly something that can easily get them fired; telling the customer off. "The customer is always right" after all.