Sim, ela poderia ter libertado os elfos domésticos, desde que os elfos domésticos quisessem possuir as roupas.
Como eu sei disso? Hermione é uma das alunas mais versadas de Hogwarts, e leu sobre a lei mágica, e os elfos domésticos são seu hobby. É inconcebível que Hermione pensasse que seus chapéus deixariam os elfos domésticos livres se não fosse o caso.
Também está implícito na Ordem da Fênix, embora seja bastante provável que Ron não conheça as leis relevantes:
‘No problem,’ said Ron. ‘Who’s that for,
anyway?’ he added, nodding at the neatly
wrapped present she was carrying.
‘Kreacher,’ said Hermione brightly.
‘It had better not be clothes!’ Ron warned
her. ‘You know what Sirius said: Kreacher
knows too much, we can’t set him free!’
Então, com isso dito, vamos analisar a única vez nos livros em que vemos um elfo doméstico se libertando:
COS Ch. 18:
Harry grabbed the diary and dashed out of the office. He could
hear Dobby’s squeals of pain receding around the corner. Quickly,
wondering if this plan could possibly work, Harry took off one of
his shoes, pulled off his slimy, filthy sock, and stuffed the diary into
it. Then he ran down the dark corridor.
He caught up with them at the top of the stairs.
“Mr. Malfoy,” he gasped, skidding to a halt, “I’ve got something
for you —”
And he forced the smelly sock into Lucius Malfoy’s hand.
“What the — ?”
Mr. Malfoy ripped the sock off the diary, threw it aside, then
looked furiously from the ruined book to Harry.
“You’ll meet the same sticky end as your parents one of these
days, Harry Potter,” he said softly. “They were meddlesome fools,
too.”
He turned to go.
“Come, Dobby. I said, come.”
But Dobby didn’t move. He was holding up Harry’s disgusting,
slimy sock, and looking at it as though it were a priceless treasure.
“Master has given a sock,” said the elf in wonderment. “Master
gave it to Dobby.”
Aqui a meia claramente pertenceu a Harry, e nunca foi de propriedade de Malfoy, e nem foi dada a Dobby intencionalmente! No entanto, mesmo com tudo isso, Dobby continua livre!
Também vemos que elfos domésticos podem lidar com roupas de seus mestres quando seus mestres ainda possuem suas roupas:
DH Ch. 12
Nothing in the room, however, was more dramatically different than the house-elf who now came hurrying toward Harry, dressed in a snowy-white towel, his ear hair as clean and fluffy as cotton wool, Regulus’s locket bouncing on his thin chest. “Shoes off, if you please, Master Harry, and hands washed before dinner,”croaked Kreacher, seizing the Invisibility Cloak and slouching off to hang it on a hook on the wall, beside a number of old-fashioned robes that had been freshly laundered.
Além disso: (COS Ch. 3)
"Yeah, Mum's always wishing we had a house-elf to do the ironing," said George.
Portanto, vemos que a liberdade dos elfos domésticos não depende do toque ou da recepção de roupas, mas sim da posse de roupas.
Este ponto é mais comprovado nos livros onde o sinal de um elfo doméstico é um guarda-roupa repugnante:
COS Ch. 2:
Harry noticed that it was
wearing what looked like an old pillowcase, with rips for arm- and
leg-holes.
Também (cap. 21)
He blew his nose on a corner of the filthy pillowcase he wore,
looking so pathetic that Harry felt his anger ebb away in spite of
himself.
“Why d’you wear that thing, Dobby?” he asked curiously.
“This, sir?” said Dobby, plucking at the pillowcase. “ ’Tis a mark
of the house-elf’s enslavement, sir.
OOP Ch. 6:
George made to shut the door to drown the
noise, but before he could do so, a house-elf edged into the room.
Except for the filthy rag tied like a loincloth around its middle, it
was completely naked.
E Dobby se orgulha de seu guarda-roupa - ou, mais precisamente, do fato de que ele pode possuir roupas: (Mais uma vez note a ênfase na posse de roupas)
GOF Ch. 21:
When Dobby had worked for the Malfoys, he had always worn
the same filthy old pillowcase. Now, however, he was wearing the
strangest assortment of garments Harry had ever seen; he had done
an even worse job of dressing himself than the wizards at the World
Cup. He was wearing a tea cozy for a hat, on which he had pinned
a number of bright badges; a tie patterned with horseshoes over a
bare chest, a pair of what looked like children’s soccer shorts, and
odd socks. One of these, Harry saw, was the black one Harry had
removed from his own foot and tricked Mr. Malfoy into giving
Dobby, thereby setting Dobby free. The other was covered in pink
and orange stripes.
De todas essas citações, vemos que manusear roupas não é o que libera um elfo doméstico, mas sim PROPRIETÁRIO de roupas.
Assim, quando Harry abandonou a posse de sua meia e foi dado a Dobby, Dobby foi liberado, embora Malfoy nunca possuiu a meia.
E assim, se Hermione renunciasse à propriedade dos chapéus, se um elfo doméstico desejasse possuir um deles, ele seria livre.
Então, por que mais elfos domésticos não são livres?
Porque um elfo doméstico não pode ir contra seus desejos mestres , e se o mestre ordenou que eles não recebessem roupas de outra pessoa, eles não podem tomar posse de roupas até que o mestre os apresente com roupas .
É também assim que um mestre pode libertar um elfo doméstico contra a sua vontade (à la Mr. Crouch), ordenando-lhes que levem roupas, que um elfo doméstico é obrigado a fazer, mesmo que não queira possui as roupas (a la Winky).
Então como Hermione poderia libertar os elfos domésticos na casa da Grifinória? Porque Dumbledore nunca fez tal ordem para os elfos domésticos que eles eram proibidos de possuir roupas, porque isso não o incomodaria se eles fossem livres. Assim, qualquer elfo doméstico em Hogwarts poderia libertar-se aproveitando os chapéus de Hermione.
Então por que eles não fizeram? Porque propriedade de roupas e liberdade é insultante para a maioria dos elfos domésticos :
None of them will clean Gryffindor Tower any more, not with the hats and socks hidden everywhere, they finds them insulting, sir. Dobby does it all himself, sir.