That you both have PTSD and respond differently; you are different people and had different experiences and responded differently. I can't really see you "turning into" her? I don't know what you see in their relationship that you are calling "dependent" and how you view you and his relationship and your "anti-dependent" behavior. No way to predict how he will respond to you, no matter what you do because your and his relationship are unique to you and he, and you are questioning what will happen in the future, and there's no way to know.

It can be extremely uncomfortable to watch another couple's behavior, especially if you know either/both of those people but that's true even when it is "good" behavior. I remember when a woman in group therapy with me was ready to terminate and she and the therapist had this beautiful, very intense (to me and the others in the group) personal conversation and I was in awe (I could learn to be/respond whole like that???) but also terrified because of the intensity. But that was about "me" and where I was at that time and maybe you are seeing things through eyes like that, where you are now and what you are thinking, etc. when their relationship and interaction is actually not germane to you.