Lady at the counter drinks slush out of my cup???

This weekend my family decided to go for a movie, we went to Jurassic world, we arrived just in time to purchase our slush & popcorn. The lady serving us poured my husbands slush which was basically all watery with no ice, I asked her if we could try another machine, as paying R30 for a cup of flavoured water with no ice when you are going to a movie is not acceptable. They lady looked into the cup & then got another cup and filled my slush half, she said she will go to the counter inside \express"counter behind the ticket line and see there. something told me to walk behind her but I had to wait in line & got there a few minutes after her. I couldn't see her & asked the other two ladies if they had seen the lady pouring my slush"