This sounds like what happened to me and my ex. We were together for 9 months and to be honest I was not happy with a lot of things he had done during our relationship, but stupidly I just kept my feelings to myself, and never let him know what I was really feeling ( it was my first relationship). I should have broken up with him early on, but I carried on with it. The more I let him get away with things the worse he treated me, but to be fair to him how was he supposed to know I was unhappy unless I told him. After 9 months I was still really in love with him but decided it was not worth it to stay with him and I broke up with him just detailing some of the things I was angry with him about the relationship; things like texting his ex, never introducing me to his friends and so on.
He said he had no idea I was feeling like this and like you was shocked at the break up. I think this is what has happened with you and your girlfriend. You do have a right to be angry with her because clearly she has never communicated what she is unhappy about in the relationship and left you in a state of confusion. This is often a reason why relationships end because communication is lacking. One may think the relationship is going swimmingly while the other is planning on breaking up.
Its scary how close you think you are to someone but are so far from them.
In answer to your question. She still loves you, and wants to tell you what she felt was wrong with the relationship.
The next step is up to you really.
Do you want her back? If so you may have to sit and listen quietly to all the things she thinks you did wrong in the relationship and to be fair you should be able to put your side forward as well.
This may be naivety in a relationship and just something you will both learn for the next one.
May be healthier to move on and have a fresh start with someone else. :)