Can a person be sued for slander because of something they wrote on their personal website?

My friend recently went on a trip to Italy. She didn't know the group she was travelling with that well. Anyway, it turns out several of the women were making money during the trip by "entertaining" the Italian men. The trip leader was encouraging it and also handling the money. My friend was disgusted and wrote about it on her personal website. Now the trip leader found out about it and is threatening to sue for slander. Does she have a case? What about freedom of speech?