McGonagall’s wording (“trapped outside Time”) suggested to me that she knows at least the basics of where Dumbledore went.
She’s just repeating what Harry said in Chapter 116:
“Dumbledore’s gone!” cried Harry Potter. “The Headmaster is gone, Professor McGonagall! The Dark Lord trapped him, he reversed some kind of trap the Headmaster planned and Dumbledore was caught outside Time, he’s gone!”
I can’t imagine she’d just accept that without asking for some kind of clarification, or putting the pieces together herself—I get the impression that the presence and general properties of the Mirror were common knowledge among faculty (what with everyone in Gryffindor having run the dungeon), though the details of Dumbledore’s plan couldn’t have been.
She’s just repeating what Harry said in Chapter 116:
I can’t imagine she’d just accept that without asking for some kind of clarification, or putting the pieces together herself—I get the impression that the presence and general properties of the Mirror were common knowledge among faculty (what with everyone in Gryffindor having run the dungeon), though the details of Dumbledore’s plan couldn’t have been.
But fair enough, I’d forgotten that bit.