I'm going to be a senior at Barnard this fall. I'm not part of the admissions committee, but I have figured out what Barnard values. First of all, your grades are not too low. The way you get into Barnard is that you demonstrate academic competency through your numbers (which are fine) AND THEN (this really important) you show your ability to think clear, daring, passionate things with your writing. You don't need to be a devastatingly wonderful writer either. It doesn't hurt if you're handy with metaphors. But what you do need to is write well, to write clearly, and to show a specific, interesting part of yourself and/or your ideas about the world. When you answer their essay questions, think of what is significant to you and fine-tune an original way of expressing it. We all feel great love, fear, admiration and longing for things: how does it affect YOU uniquely?
Do not fret so much about your grades and extracurriculars. Sometimes an extracurricular is so special that that is what draws the attention of the admissions people. But sometimes it doesn't need to be. You just have to reveal that beautiful, honest part of yourself in your essays and they'll know what you did was special. Another tip, though: these essays are not a confessional either. Do not write about the darkest, most traumatic or gruesome time in your life. If you must, tread carefully. Remember emotional truth can be found in smaller, quieter things, too.
Of course, don't skimp on your grades. Work hard, but also don't stress about imperfections.
Don't worry. Feel good. Write boldly when you apply to Barnard. All right?