What question specifically would you like addressed?
Thank you for clarifying.
It may be possible that she was changing all along even while you were together. You may have missed the behaviors or she may have put on a front. Like you said, there were problems prebreaking up. Maybe she was seeing someone on the side?
People can change (how fast it depends on each individual) She may have had difficulty communicating with you and is resorting to only replying to your texts because it is safer for her to do so.
It may be fair to at least have her tell you what had transpired in your relationship to have led to this.