i think (and im just guessing here (id give myself a chance that im correct 70%) the following has happened.
girl has a past with abusive and dominating family and ex.
Girl now is in a relationship with a "nice guy" and loves it. However she always feels that something is missing. The feeling of deep love (which is not an obvious feeling for many people, me for example) is unknown to her. The "love" she feels for him is to a great deal affection and thankfullness for being treated so well.
Now you should understand that most women like/need to be dominated to an extend. This usually involves sexual domination. I guess this is not something you have been doing. She is expecting it and probably to some extend wanting it (at least in the bedroom).
Then she left you because she wanted to get that feeling back.
Then she notives how much she is missing you. I think this is actually where we feel love the most: when the one you love is away and your heart hungers for them to be there again.
And i think this is where she realised that she does not only feel affection and thankfulness but that she really loves you.
This is where she also realises that she ****ed up big time and will never have the chance to be back with you again.
And then the hate for herself for not noticing it sooner and being so "selfdestructive" kicks in.
Additionally she probably feels she deserves no better - but you do.
And if i am correct with it, i think that this is rather sad.
If you think I am insulting you with my post or bashing you: You do not get the point.
I am not here to insult or bash anyone. I offer up my free time to help. Take from my post what is useful to you.
If you are angry about my post or myself, then please stop and think how that happened. Usually that is the way the brain responds if a critical belief system is challenged (its called cognitive dissonance). If you have trouble with it please answer in the thread. I will come back to you.