女 appears in many compound characters, where its meaning is often very clear. For example 妹 meaning "younger sister" is a combination of 女 (meaning "WOMAN") and 未 (meaning "Not Yet"). So "Woman + Not Yet" means "Younger sister". Your younger sister is not yet a WOMAN. Not all combination characters are as clear as this, but the ones involving 女 (WOMAN) very often are clearer than most.