Matthias was silent for a moment, he could see the pain etched in her expression and her eyes. "If he was at peace after so long, then perhaps he wanted to rest. Of course you are sad for losing him, but you look ... as though you feel guilt, as well."
He was uncertain, of course, whether or not she did feel guilty, but her body language showed that. And, while he could understand her grief, he could also understand that her Alucard was a vampire, likely as old as Matthias himself. And that some vampires felt the urge, after a while, to seek rest, either permanently or for a time.