Harry couldn’t see Confundus!Quirrell’s CEV in the mirror (the conversation with Dumbledore’s family.)
What the man might be seeing there, Harry could not tell; to Harry it seemed that the flat, perfect surface still reflected the room behind it, like a portal to another place.
So I take from that the Dumbledore in the mirror was real, and not a victory fantasy of Quirrell’s, since Harry could also see it.
Also, Dumbledore mentioned how he laughed when he found out that Harry was a good version of Riddle, which many readers have taken to refer to this scene in Chapter 17:
Dumbledore started laughing. Laughing a lot harder than Harry would expect, almost howling. It seemed positively undignified. An ancient and powerful wizard ought to chuckle in deep booming tones, not laugh so hard he was gasping for breath. Harry had once literally fallen out of his chair while watching the Marx Brothers movie Duck Soup, and that was how hard Dumbledore was laughing now.
“It’s not that funny,” Harry said after a while. He was starting to worry about Dumbledore’s sanity again.
Dumbledore got himself under control again with a visible effort. “Ah, Harry, one symptom of the disease called wisdom is that you begin laughing at things that no one else thinks is funny, because when you’re wise, Harry, you start getting the jokes!” The old wizard wiped tears away from his eyes. “Ah, me. Ah, me. Oft evil will shall evil mar indeed, in very deed.”
This was a scene that Quirrell was most definitely not present for, and thus the fact that Mirror!Dumbledore knows about it further suggests that Mirror!Dumbledore was not simply some CEV-illusion of Quirrell’s.
Harry couldn’t see Confundus!Quirrell’s CEV in the mirror (the conversation with Dumbledore’s family.)
So I take from that the Dumbledore in the mirror was real, and not a victory fantasy of Quirrell’s, since Harry could also see it.
Also, Dumbledore mentioned how he laughed when he found out that Harry was a good version of Riddle, which many readers have taken to refer to this scene in Chapter 17:
This was a scene that Quirrell was most definitely not present for, and thus the fact that Mirror!Dumbledore knows about it further suggests that Mirror!Dumbledore was not simply some CEV-illusion of Quirrell’s.