I get very confused when I read this. At first I thought she was in a forest, but upon reading the second sentance I realise that this is not true.

"These doors..." I am supposing are the "giant timbers" she is opening to get into a room of sorts. I imagine the Lion, Witch and the Wardrobe here and being on the forest side walking back into the room.

If that is what you are trying to portray then rewording the first two sentances would good. At this moment I've not a hint to give to help. Sorry.

Silence greeted her. ( I like this sentance)

"Her cold boots tapped onto the granite floor and the echo of the soft clicks produced by her heels suggested the room to be more expansive than on first inspection."

How about, "Her boots tapped onto the cold granite floor..." as I can't picture boots being cold unless it was snowing out and even then...

"She noticed her target at the end of the room and she watched as the Queen, stationed in her throne, allowed all air to expel from regal lungs as if to prepare for the inevitable."

Not sure who the target is, the Queen or someone else, but I'd keep reading just to see.

but i agree on the confusion conclusion.

'these doors' sounds like a pov error maybe just 'the doors'

she makes a mockery of a fake defense. this seems to be a contradiction. if the defense were real, but weak she could mock it more efficiently maybe. if it is fake than perhaps she is being made a mockery of herself.

'the faces of all present' are those faces surprised she made a mockery of their defenses or were they 'all present' because they were expecting her. all present sounds awk to me, but i hav no formal basis for that opinion.

agree with no cold boots maybe
Her boots tapped on the cold granite floor, the heels produced echoing soft clicks, suggesting the room to be more expansive than on her first inspection

This is it. I almost think this is unnecessary. Since we don't know what this is, and we don't know what "it" is, this statement means nothing to me. It's a wasted line, in my opinion.
She pushed through the timber giants easily. These doors moved softly as if they were a weightless mirage, a fake defense with which she effortlessly made a mockery Okay, you've already lost me. I, too, thought the timber giants were trees. Then the doors moved as if they were a weightless mirage. But what sort of mirage has weight? I don't think your metaphor works here. And how is that weightless mirage a fake defense? And how does she make a mockery out of a fake defense? I think what you're trying to say is that the doors were supposed to have the appearance of being sturdy, timber doors, but somehow she's immune or can overcome their magic. This could definitely be clearer.. She stood a moment and watched as the gloom of dusk flowed through the windows before her and spread over the faces of all present.Okay, maybe a line of what she's entered into? I've still got the image of a forest in my mind. It's a house of some kind, but what kind of house? A castle? A long house? A wood shingled bungalow? A log cabin?
Silence greeted her.
Her cold boots tapped onto the granite floor and the echo of the soft clicks produced by her heels suggested the room to be more expansive than on first inspection Okay, we haven't gotten the first inspection so I have nothing to compare it to. What is she seeing? What sort of room? Why are her boots cold? Also, I found this sentence to be a bit verbose. The sentence structure is roundabout and awkward with the use of "clicks produced by her heels". She noticed her target at the end of the room and she watched as the Queen Again, very wordy. If the target and the queen are one and the same maybe just cut to the chase?, stationed in her throne, allowed all air to expel from regal lungs as if to prepare for the inevitable.

There's definitely tension here. I want to have more insight into the character. I don't even know who she is. I have no idea what genre this is. The presence of the queen, boots, stone floor, and timbers suggests fantasy, but I really don't know that for a fact. Nor am I clear on setting. First I thought it was a forest, then maybe a castle, but then there's just one room, which was odd to me.

I think you can afford to slow down here and lay a little groundwork. Also, if the sentences were more efficient you could move the story forward a bit faster, and provide a stronger sense of character, milieu, etc. earlier on.