Attitude from cashier

I was at Shoprite at Protea Glen ext 16 (Glenridge). There is a cashier her name is Mamello. I don't think she has a right to tell staff to skip me while I'm still in queue. She has attitude and bad looks. I'm a customer too. How she tell staff to skip me without telling me that till is only opened for staff only. I went to pay to another till, when I go out there is customers. Please advise what kind of treatment are we getting? Or my money does not add value in your shop. I need feedback regarding this.