Star doesn't press her when she looks down, letting her hand drop from Moon's face. It's not because she doesn't care. It's the same reason she didn't pull Draco into her lap. This step isn't hers. It isn't allowed or right.

She gives them the door. But she can not be the feet to walk through it.

But this is her sister, and for that alone, there is a very minute squeeze of her hand.