Somnus wasn't expecting to be handed over a carte blanche. He's curious, indeed, but he's also aware that they are both in a pretty precarious position right now when it comes to emotions, and while she seems to have a handle on it he kinda needs to make sure he's still got someone by his side to talk to. Losing her to her own guilt would defeat the purpose.

"You're under no obligation to answer me, of course." He's aware she doesn't need his permission, but it doesn't hurt to play nice.

"But what did you mean when you said you would not have a long life?"