I am so sorry that happened to you. That's terrible. She's right, you were completely ignored, and unseen.

As for the attachment, it's totally normal, especially at the time you are describing. I have been seeing my T for a year and a half and it's only been in the past two months that I have really started to feel "attached". Prior to that point, she could have left and it wouldn't have mattered much. But it is a little shocking and scary when it happens, especially if you don't normally allow yourself to get close to people.

The best thing you can do (and the most terrifying) is to tell her how you feel. It will help the feelings be not so intense, and she will be able to help you through understanding what you feel and why.