Siffleur may not want to hear more, but Valdis certainly does. His mother has moved on though and she's an intruder upon a moment between family. When the woman reaches for the kitten, Valdis doesn't hand him over.

"Promising to not hurt Siffleur is not the same as promising to not hurt anyone else."

She's not holding the kitten hostage, merely compelling the woman to actually address the other piece of her terms.