Well, if she does everything, except for making things unhappen, then that'll still be good. So she doesn't have to make things unhappen.

He holds on to his blanket with both hands, and wishes with all his might, squeezing every expression out of his face.

Nothing happens.

Holds on to the sheets again. Squeezes again, with his face tight and his stomach as well.

Nothing.

Then with his face, his stomach, and every muscle in his body.

Nothing happens... Until he relaxes.

He feels a tiny presence in the room. Somewhere near his face. He's not sure about this sensation. He can't see anything so maybe he has squeezed himself so hard that now he's feeling all sorts of stuff. His face is certainly red. He can't see it but he can feel the heat.
He turns his face to the desk near him and he sees.

He sees a tiny woman.
Not blond, but brown haired.
Not young, but not like his grandmother either.
No ballerina dress. Light pants, old brown boots, and a comfortable jumper.
Not a stupid look, but relaxed eyes, with a really soft smile. That's why he doesn't jump out of the bed when he sees her.

He looks at her hands. She's not carrying anything. Where's the magic wand?
He doesn't say it yet. He looks at her, into her, through her, and around her.
He's not dreaming. He's not scared. He's not necessarily happy. He's just looking.
Is this a fairy?