Should I say that the request of the old woman did not come as a surprise to either of them?
Sango especially had expected something like this to happen.
Being the careful and observing type that she has shown to be, it was only appropriate in her defence that she would seek out their strength.
"Are you telling us to die in exchange for information that we can easily wriggle out of you?". Sango mused, his words coming off as a threat and advice to the old woman.
But he wasn't wrong with what was said.
They have no information on this so-called beast the old woman is referring to. Accepting to fulfil her request without any knowledge of what they are walking into, is another type of death sentence in their defence.
The old woman knew that. She knew how high of a request she was extending their way, that is why she remained silent and hesitant to Sango's question.