The part of him that's still Sirius Black is buried in deep, now; curled in close into itself to keep itself from fading away entirely. It means there isn't a flicker of concern where there usually would have been, at the false smile on her face. It means he doesn't move away instantly the way Sirius Black might have.

"That's sweet, Lils." The nickname doesn't sound anything like affectionate on his tongue, "But there's-- really not much to say. I'm sorry you miss me, but I don't-- want to come home. Besides--"

The twist of his head could be like he's checking a clock. Isn't, and she's likely clever enough to know that it's an indication of the general direction the snake is in. Merdraut didn't know exactly how well Lily Potter knew Sirius Black. Voldemort, for all he's so much stronger now, doesn't realize how much she'd still care despite being so obviously rebuffed.

"--I'll be heading out soon. I doubt what you've planned to say will be quick. But there really isn't anything you can do to convince me. I'm sorry."

The last reply sounds almost genuine.