Dream about someone slapping someone is a metaphor for the results of your hard work. You may be taking on too many responsibilities and working too hard that you are not catering to your emotional self. You may have compromised your own beliefs and values. It is a premonition for a rash decision that you are making. There is some unrest or uneasiness within which needs to be addressed and resolved immediately.
Someone slapping someone dream is unfortunately some confusion in your thought process. You are lacking in a particular nutrient. You have bitten off more than you chew. This dream is sadly your anxiety over money matters and financial security. There is a situation that you are trying to avoid.
If you dreamt about someone slapping someone:
The difficulty is probably associated with an old pattern of behavior that is limiting your emotional expression. Perhaps it would help to spend some time alone, as this is the fastest way to make progress and change things for the better. Be at peace with yourself.