I think that it is WONDERFUL that you're going to college! Maybe she is an old fashioned woman who thinks that a wife's life should revolve around searching for a husband's missing socks and being a trophy wife. Let her know that women can have ambition and that looks fade but intelligence doesn't.
You're doing the right thing and it will feel WONDERFUL once you've accomplished what you want to and doing what you want to do. I know people like your grandmother, she sounds a lot like my mom. No matter what you do, it really won't make them happy, they will just move on to something else to nag about. Just try to keep positive people in your life.
Bottom line: It's YOUR life, do what makes YOU happy!