Dear Brianna,
You could let your friends know that it bothers you to hear them swearing, and maybe they'll be more aware of their language when you're around. The girls in your class may use swearing to show how grown up they are or just to show off. You can't control how other people act, but you can make decisions about what you do and say.

Dear Brianna,
You could talk to your friends and ask them why they swear. Say that there are plenty of other words they could use and swearing is just not necessary. Tell them that it is not cool to swear and that you don't like it when they do it. See what they do when you ask them to stop.