Unlike most of the room she knows Harry well enough that even him scaring a Dementor, no matter how surprising, wouldn’t make her personally afraid of Harry; she might be worried about what trouble he could cause but she knows perfectly well that he wouldn’t do anything to her. Besides it was less of a surprise for her since Dumbledore already told her Harry had developed a new charm.
~And furthermore, in her post-Azkaban-breakout council with Snape and Dumbledore, Dumbledore explicitly told her that Harry has unique magics that would help orchestrate an Azkaban breakout. She doesn’t know the specifics of Harry’s ability, but Minerva would certainly be able to deduce that it has something to do with Dementors.~
[EDIT: Apparently I did not read your last sentence before deciding to post this.]
There was a distinct body-hitting-the-ground-with-a-thuddish sort of sound.
“Thank you for taking care of that, Quirinus,” said Dumbledore to Professor Quirrell, who was now standing above and behind the unconscious forms of the three Aurors. “I confess I am still feeling a bit peaky. Though I shall handle the Memory Charms myself.”
However, both McGonagall and Snape know that Harry has developed a charm which can affect the behavior of Dementors:
Albus nodded grimly. “Unfortunately there is now another wizard who laughs at impossibilities. A wizard who, not long ago, developed a new and powerful Charm which could have blinded the Dementors to Bellatrix Black’s escape.
Unlike most of the room she knows Harry well enough that even him scaring a Dementor, no matter how surprising, wouldn’t make her personally afraid of Harry; she might be worried about what trouble he could cause but she knows perfectly well that he wouldn’t do anything to her. Besides it was less of a surprise for her since Dumbledore already told her Harry had developed a new charm.
I agree that her being afraid of Harry isn’t something I would expect, but her comments make me think she isn’t taking the situation seriously.
~And furthermore, in her post-Azkaban-breakout council with Snape and Dumbledore, Dumbledore explicitly told her that Harry has unique magics that would help orchestrate an Azkaban breakout. She doesn’t know the specifics of Harry’s ability, but Minerva would certainly be able to deduce that it has something to do with Dementors.~
[EDIT: Apparently I did not read your last sentence before deciding to post this.]
Isn’t Harry’s destruction of a dementor public knowledge at Hogwarts
Edit: Oops, missed it.
Only Quirrel and Dumbledore know of it, since even the three accompanying Aurors were False-Memory-Charmed.
We don’t know what the cover story was that Dumbledore thought up to justify the lost Dementor.
« And so remained only Harry, Professor Quirrell, Headmaster Dumbledore, and an Auror trio.
It would have been better to get rid of the trio first, but Harry couldn’t think of a good way to do that.» from chapter 45
Harry ensured that very few people saw him destroying it.
I believe that the Auror trio was memory charmed.
-Chapter 46
However, both McGonagall and Snape know that Harry has developed a charm which can affect the behavior of Dementors:
-Chapter 61