Dressing up as a Domme for a moment and sneaking in...

Most subs/slaves crave their Dom's attention, is she perhaps doing this because when you are mad you give her that attention, and ignore her at other times? Think about positive and negative re-enforcement.

Oh and everything which Wolfscout has said...

cariad

(MasterDarkOne - a spanking such as you describe sounds to me like the perfect reward...)