I would think that if this person is your "Spouse" that you would have decided earlier in your relationship that she did or does love you.
If you are referring to "Loving" in the "Make Love" sense of the word, that is sometimes tough to discern. There are subtle physical changes that happen when a person is excited and or climaxing. Blood flow to the brain increases and can be seen in the neck, eyes dilated, cheeks flushed etc.
I am not sure which way you meant this question.