Shouted at by Wakaberry worker

My husband and I have always been faithful Wakaberry customers. One day we went to the King Pie that is next to the Wakaberry at the mall and we planned on going to Wakaberry when we were done with our pie. I got a knife at Wakaberry to cut the pie when the woman working there came and started shouting at me, telling me that I can’t use the plastic knife because it’s for her customers only. I explained that we were faithful customers but she just continued to shout at me. I was so shocked by this behaviour. I offered to give the knife back (because I know they wash and reuse the knives because I often find old food on them) and she shouted that she doesn’t want the knife back. We did not have Wakaberry like we had planned to because we refused to go there after someone had been so rude to us over a knife. Why would someone choose to lose customers over a knife?