Hi, Daniella. Ken is absolutely right. Your friend is doing a great thing by volunteering to learn more about what she hopes to major in in college. She is also making great connections and possible getting wonderful recommendations this way. The college will see her commitment to her studies and her community as well as know that she have credible references.
For you, you should still volunteer an/or engage in extracurricular activities even if you're not sure about your major. It will certainly help you determine what you like and don't like while at the same time help you build strong networks who will voice your commitment to your community when you apply to college. This is a big deal for a college institutions and for other organizations you may want to join while in college. It shows a positive light on your character. Good luck and have fun!