What risk?
Joseph had already come to grips with the situation.
Who was going to stone her?
Deuteronomy 17:6
On the testimony of two or three witnesses a person is to be put to death, but no one is to be put to death on the testimony of only one witness.
When she declared ‘let is be done to me according to thy word...’ she had no idea what Joseph’s reaction would be... and no idea if she might meet the fate of an adulterer.