What would happen if I break my lease?

Generally speaking, when you sign a lease with a roommate(s) you are all separately responsible for all of the rent. This means that your roommate will be responsible for paying the entire rent in your absence. She could take you to court and sue you for your half, but whether the judge rules in her favor is unknown. The right thing to do would be to find someone else to move in and share the rent with her, keep trying.