I'm not exactly clear about what you are asking. If you want to know: are mother-in-law and daughter-in-law contradictory terms? No. They are distinct, non-ambiguous terms. But if you want to ask: in other countries and cultures, is it common for a mother-in-law and a daughter-in-law to have conflicts? In my experience, in the US, it is not uncommon for a mother and her son's wife to disagree on many topics (raising children, where to spend the holidays, etc.).

do you mean a contration/compound word? When you put two words together to make a word.