How to use "vague" in a sentence

The vague, shadowy shape of her under the covers, in the darkness, was a talisman to ward off loneliness.

It was such a tentative smile, such a vague ghost of all the broad warm smiles she remembered, that it broke her heart.

Her face was pale and thin, and her long suffering in the asylum had affected her mind, so that her expression was vague and her memory confused