Sorry to hear your munchkin is sick. That's a nasty bug that's going around.
Make no assumptions with your spouse. Call ahead and let her know the situation. She can agree or disagree and your child doesn't get stuck in the middle.
Anything you say to her will NOT be heard. Repeat that constantly. Getting in verbal warfare does nothing but fuel meanness and hatred. Nothing you say to her will be heard. In fact, the LESS you say the more she'll notice. You know how hard it is for people to stay quiet when there's silence? Extremely. Be the quiet one.