[He, similarly, seems different with her, than when he is speaking to Gwen. As if the height that he so carefully ensures is used to full force with humans is relaxed - not slouching, but the tenseness in his muscles releases.]

There are ways to be vigilant, but unfortunately it is unlikely that you would know for certain unless a spirit pulled itself through the veil. If - your lady - [And he says the word with a sliver of distaste, though he attempts to hide it in courtesy] - wakes and is acting strange, or not herself, then it may have approached her in her sleep. If you have any reason to doubt, you may come to me.