I think maybe bursting out crying and accusing him of leaving you was a bit OTT because it was out of proportion to what he said, and assumed things that he did not say. I don't think that means anything bad about you except that this is clearly an area that is very sensitive. I overreact emotionally sometimes and I do understand that certain triggers can hit you really hard and it's difficult not to get caught up in an emotional flashback.

Do you have a valid reason for being upset? I don't think you necessarily have a valid reason for catastrophizing based on that one comment, but if you have attachment issues, your reaction is not illogical when viewed through that lens. By "not valid" I don't mean you are wrong for having these feelings, I just mean that I don't think the intensity of your reaction is an accurate reflection of what was happening - but instead a reflection of past abandonment.

ETA - Regarding apologizing... I do sometimes apologize in these instances if I feel like I behaved unfairly to the therapist. I don't apologize for being upset, but for taking things to the next level and acting like she's an abuser instead of someone who is trying to help me. That's just my personal preference for how I deal with my own "tantrums." She has never asked for an apology or been punitive or anything, but she has said she appreciates that I apologize for some of my OTT responses and that I am willing to talk things through with her.