It's not black and white. Your latching on to others wasn't just bad, like you felt it to be, but you did get something from it (or you wouldn't have done it) as T points out.

Translate that to how you're feeling now, threatened. What did you say at the beginning, "felt i had no issue as such"? Well now look, "turmoil". Isn't that nice? T can't say you're all cured and throw you out.

There's always sides to everything so start looking for ones that aren't obvious to you. Yes when you're "happy"/pleased you can imagine that there will be unhappiness/anger/threat somewhere but what about less unhappy or unpleasant, more rounded feelings?

Think about your T and imagine her thinking about you :-) and what you're telling her. She's neither expressing the feeling that you are all cured and perfect at relationships or that you are horrible at them, she's just pointing out that there are other feelings in there, disappointment. But she's not any of those feelings, she is just going along being herself. Even keel. She's not caught up in your "whiplash"? She's trying to help you get to where she is, in yourself.

I use to try to observe my T sometimes (third person) and suspend myself with my roiling emotions during a session. They're calm and quiet, and trying to imagine what my T was thinking and feeling helped calm and quiet me sometimes too.