Amane's less of what and more of oh shit, so she probably knows what it... is. To an extent. Her 'attacks' don't seem to be working, and the creature is untangling itself from disarray, nonchalantly reaching down with its... arms... at Amane.

She backs up as much as possible, before it sticks two of its fingers into her mouth, black fingernails scratching Amane's face. For some reason, the girl goes completely limb at that, not even willing to fight back- or maybe, just got paralyzed in the context of the dream? It's tough to tell. In any case, the monster leans over, stretching her mouth, and... does a feat of completely bullshit dream logic.

It forces its entire form into Amane's mouth, being swallowed into whatever bottomless pit of a body her dream expects her to have. Amane does squirm, but other than that, the monster's descent is incredibly fast- and the Cartesian Garden turns into something of a monstrous lava landscape, stretching across the whole dream.

If Amane knew you were there, Rose, she'd be so sorry for letting you witness that.