Sthena left his chambers allowing the maids to bathe and take care of Perdita because she needed it.
The reason for her bathing was not only to keep her clean, but it was also a way to keep her head cool so she can think straight and perhaps remember when she had bitten and drank his blood.
He had his reason for not telling her exactly what she did. Suddenly telling her that she had bitten and drank his blood after many years of vowing not to take blood that was not that of a cat would break her spirit.
She was a strong-headed woman and he noticed she always held unto something very dear to her with all her might. She always remained true to her words. So finding out from him she broke her vow in her unconscious state will leave her blaming herself each time she remembered it.
However, if she remembered it herself when her head was cool and clear, she will be able to think it through and take in the outcome with a calm heart.
