My daughter is being hared!?

My daughter is a senior in high school. Three girls in her cl have a crush on my daughter's boyfriend and have been trying to make them break up by slandering my daughter. They are making up stories about her, and telling others in her cl. She is so upset that there are days she doesn't want to go to school. Her boyfriend has told these girls to stop it, but they continue. I have gone to the school, and they have told my daughter that she can come down to the office to cry, talk, etc whenever she needs to. The lies have not stopped. I am thinking of going back to school tomorrow, and ask them to confront the 3 girls to tell them to stop, or we will press charges. What do you think?