Ditto to the above. You may stumble into a history class or an English class and decide that you have an entirely different passion! Currently, the field has alot of issues. I don't need to repeat them here. I have been super fortunate (and beyond lucky) to have been able to garner external fellowships during this horrible climate. But these fellowships came with many sacrifices (social, sleep wise, being single and in my 30s, etc) and often felt as if I was a pigeon fighting on the ground for breadcrumbs of money.
With the above stated, I do want to make some notes regarding the current choice you have. Barnard is great. But do look at the dollar signs. Entering grad school with debt can be hard. The top PhD programs typically offer students 4-5 year funding and health insurance plans. However, alot of these packages may not be enough to live in expensive areas (look at Columbia and NYU stipends). Sometimes you may have to pay out of pocket for a publication, for conference attendance, etc. Some have already begun (thank God like my program) to make up for this by offering summer stipends, conference funds, etc. But it sometimes takes months to get reimbursed and I have gone at times several months without insurance or even pay due to administrative issues. What I am trying to say is that it is good to start grad school with some dollars in the bank for hiccups along the way. Something to consider is the fact that if you are to attend Barnard, it might be quite some time until those debts get paid off. The system is crummy but yet we are all here...:/