A mother-in-law is read as the authority of another family and the wish to be accepted by it. Dream books link her to expectations, boundaries, and comparisons with your own mother. A friendly mother-in-law is read as feeling welcomed and at ease in a new role. Arguing with her, or being criticised, is taken as tension about being judged, or a boundary that needs to be set. A mother-in-law moving into your house is read as outside influence entering your private life. Dreaming of a mother-in-law you do not have is read as worry about fitting into a new group. It can help to notice whose approval you are waiting for right now.
Does the traditional reading fit your dream, or did it mean something else to you?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.