The meaning of seeing your mother-in-law in a dream is that there is an unresolved issue or inner worries that you need to work on. Your waking life relationship with your mother-in-law will prevail in this interpretation.
You may look in dreams interpretation for other symbols :
Mountain : The meaning of seeing mountains in your dream represents many obstacles and major challenges that you have to overcome. In you are on top of the mountain, ... html">
Mourning : The meaning of dreaming that you are in mourning is that you repress your pain. Maybe something bothers you more than you realize. You need to express ...