I guess I don't really see the point. You talk of what you'd want from the session as though you're talking about confronting an abuser. Your former T is unlikely to say anything you want to hear under those conditions. There's no hope or possibility of a reconciliation, so there would be no opportunity to work anything out with her that you couldn't better work through with your current T. It just feels like there isn't anything to gain except an amorphous sense of closure--which might even backfire and just reopen wounds.