Thanks, upvoted for quick response.

The quote is this:

And in the same instant the Mirror changed, no longer showing Harry the reflection of the room, showing instead the form of the real Albus Dumbledore, as though he were standing just behind the Mirror and visible through it.

The real Dumbledore's face was set, and grim.

This doesn't sound like AD is stuck in the mirror, but I think this rules out QQ being in it. Both would seem to be counter to the story, as it can't end just yet.