I don't believe to two seconds that there were no indications that she could do this kind of thing. My guess is that you never knew she could do this kind of thing *to you*. You mean to tell me that she never showed that she was self-centered, and didn't take responsibility for her actions in all the time you were together? Seriously? Never turned on one of her friends? Never did something bad and then blamed others when she got caught for it? Never acted like she was entitled to things she didn't earn? Never?
The problem is that people need to understand that you really don't know someone until you see them in a crisis situation, and that can take years. However, watching their general behavior can tell you much. Most people will rationalize their SO's bad behavior by saying "she would never do that to me though".