Grey's Anatomy Question?

At the end of Grey's Anatomy when Christina and Burke did not get married and we saw Christina back at the apartment and she was talking to Meredith about how all Burke's stuff was gone and then she started crying and said "I'm Free"...what did that mean? I thought she was sad that she lost Burke, but my friend thought she was happy because she was finally "free". What do you think - was she happy or was she sad?