"...I see." They have an inkling about the circumstances of that, but that's neither here nor there. Right now, there's no reason to dig further.

"All right. So for the safe - do not let anyone drink from you unless we have arranged it together ahead of time." Either for a single or for multiple occasions. "Now, consensual...

...what would you not want, assuming it involves someone drinking your blood without killing you? Persons, acts, circumstances..."