She's so, so sorry but maybe she's being a bit rude or judgemental somehow because she's sure she misheard his last words.

"Sell my soul...? Um. W--" Give her a few seconds because he managed to get her become speechless. Quite an achievement.

Did she hear that properly? She doesn't think she heard that properly because that sounded kind of bizarre and a little bit uncomfortable. "I must have heard you wrong there but I. I didn't know that could happen if you could do that."

Nor understand why anyone would want to do that, to be honest. She's rather certain that the average being needs a soul to continue living.