Hi coldmist,
I'm so sorry to hear about your breakup. These are very intense relationships, no matter how long they lasted. The bond formed is very loaded, and I think all of use know what that's like. It is extremely painful to have that bond broken and it can be tremendously confusing too. My breakup with my ex was a surreal experience and agonizingly painful. So, I can understand. It's very hard, and it will take some time to heal. We're all here to support you, though. Hang in there. This will get easier as you go along in healing.
I can imagine that your GAD makes it very hard to deal with the withdrawing by your ex. The withdrawing is, unfortunately, a common feature of the disorder. It is a response to the trigger that is emotional intimacy. Please know that this is not your fault. It's not because you aren't good enough and it's not because of something you did. It's just part of the disorder. Fears of abandonment are also a core feature of the disorder and it is likely why your ex was so upset about not speaking to her. I think most of us have done similar in frustration at some point. So, please don't be hard on yourself about it. These are very difficult relationships.
I think it's great that you are working with a therapist. My own therapist (T) was hugely helpful to me in my own healing. Very smart move!
It's common that our ex will also split us as a way for them to deal with the overwhelming emotion that they are feeling when triggered. This is likely what you are experiencing with your ex suddenly thinking that you are such an awful person and saying such hurtful and untrue, distorted things. We often refer to this as being "painted black". It is very hard to deal with and it truly hurts to have someone we care about turn on us like this. Please remember that this is the disorder. It is not you. That's so important.
Hang in there, coldmist. Things will get easier in time. Posting here is a great way to get support from people who can understand what you are going through. Keep working hard in therapy too. Healing will come in time. For now, be sure to take good care of you. That's so important when we are this hurt. Be gentle with you. You deserve it!