Several years back I taught knitting classes. One night a lady drove her friend to the class and sat in but didn't actually participate. At the end of the class I asked if she'd like to buy the pattern, one of my designs. My intention was to charger her for the pattern but not the class. She said, "No, I'll just copy Susie's." That made me so mad I replied, "Well, then I'll only charge you for the class." She didn't object but you should have seen the expression on her face.
You did the right thing. If she didn't want to pay for the class she shouldn't have come.