She appears to refer to it when she is talking to Piro, not that he would have any idea what she meant. Confirmed, if that incident is what she's referring to, if she meant Ed's weapons killed her at the time, and if all that is the truth. Being just about devoid of any detail whatsoever, and said to someone who doesn't know any of it, is not a very compelling confirmation of anything.
All we know is Meimi appears to have reacted to whatever happened. Later, that schoolpeople started forgetting about her, Ping was still trying to find out where she went to, the CoE staff had all sorts of ideas about where she was and in what state, Piro had been previously told she'd be at the Analogue Support Facility. And that she was very much not dead when Yuki arrived after a week end a half.
The short of it is we do not know what happened the instant after she waves at Ed any more than we're informed of what went on with her between then and when Yuki shows up. The details are naught but perception and inference. Did she toss a life as in released to respawn free of the aggro, perhaps. Perhaps not. Did she confirm anything, not really.