Did Dumbledore suspect Rosmerta immediately after Ron's poisoning?

Question

Half-Blood Prince chapter The Lightning-Struck Tower

“Very gratifying,” said Dumbledore mildly. “We all like appreciation for our own hard work, of course. But you must have had an accomplice, all the same . . . someone in Hogsmeade, someone who was able to slip Katie the — the — aaaah . . .”

Dumbledore closed his eyes again and nodded, as though he was about to fall asleep. “. . . of course . . . Rosmerta. How long has she been under the Imperius Curse?”

“Got there at last, have you?” Malfoy taunted...

...“So poor Rosmerta was forced to lurk in her own bathroom and pass that necklace to any Hogwarts student who entered the room unaccompanied? And the poisoned mead . . . well, naturally, Rosmerta was able to poison it for you before she sent the bottle to Slughorn, believing that it was to be my Christmas present. . . . Yes, very neat . . . very neat . . . Poor Mr. Filch would not, of course, think to check a bottle of Rosmerta’s.

Isn't it strange that during this particular conversation with Draco, Dumbledore would ask the questions, supply the clues, then give the answers himself?

Almost as if Dumbledore was certain of the answers long ago.

All the clues Dumbledore told Draco were available to Dumbledore looong before the scene at the Astronomy Tower.

After the poisoning of Ron, did Dumbledore already have a good idea that Rosmerta is under the Imperious Curse?

Isn't it strangely convenient that Dumbledore and Harry (under cloak) walked to the Three Broomsticks where Dumbledore made it a point to greet Rosmerta and inform her of his fake destination?

Half-blood prince chapter The Seer Overheard

...“But what will people think when they see you leaving, Professor?” Harry asked, his mind on Malfoy and Snape. “That I am off into Hogsmeade for a drink,” said Dumbledore lightly. “I sometimes offer Rosmerta my custom, or else visit the Hog’s Head . . . or I appear to. It is as good a way as any of disguising one’s true destination.”

...“Good evening, Rosmerta, good evening . . . forgive me, I’m off to the Hog’s Head. . . . No offense, but I feel like a quieter atmo- sphere tonight. . . .”

Dumbledore wanted people in the castle to see him leaving, that explains walking in plain sight towards Hogsmeade.

Why conveniently tell Rosmerta (and nobody else) his fake destination?

Answer 1

The simple answer is no, Dumbledore did not actively suspect Rosmerta. Consider these points:

• The only way Rosmerta would be helping Draco is with some illegal Dark magic, like the Imperius Curse. Had Dumbledore known, he would have seen to it that the curse be lifted. That could have been done without implicating Draco.

• He would not have trusted Rosmerta to send for help from the Ministry when the Dark Mark was set over the Astronomy Tower.

• About his colloquy with Draco - how many times do we ask questions then, after verbalizing them, immediately realize the answers? So it was with Dumbledore. All the events of the school year plus seeing Rosmerta in Hogsmeade was put together in Dumbledore's mind as he asked the questions, thus allowing him to answer them reasonably.

I understand the need to think of Dumbledore as omniscient, but he isn't. He's brilliant. The lessons with Harry in earlier chapters of the Half-Blood Prince show us that Dumbledore does a lot of guesswork. Stringing together Rosmerta's role in helping Draco was another example of his brilliant guesswork.

Answer 2

I believe so. He knew the whole time that Draco was trying to kill him but had to pretend not to know so that the events play out.

I am pretty sure with his clever mind, he would have put the necklace and poisoned mead together much sooner. That is assuming Snape didn't tell him first!