In my language, the title of Battle Hymn of the Tiger Mother has been translated as Боевой гимн матери-тигрицы, which translates to "Battle hymn of the mother-tigress". I think Ms Chua meant the word "tiger" as a noun, not as an adjective. So, in this case "mother-tigress" would be right. Is this correct?
There are a couple reasons: first and foremost, the term “Tiger Mother” was already in common use, particularly among Chinese-Americans to describe the kind of parenting style that Chua writes about in her book.
Second, is that in English, “Tiger Mother” has Tiger modifying mother and describes a mother with the attributes of a tiger (the term is a bit hyperbolic, intentionally so). “Mother Tigress” on the other hand would be a tigress who is a mother, and would be more likely applied to an actual female tiger than a human being.