Complex sentence: Bruriah made light of the Talmudic assertion that women are "light-minded" Rashi (Kiddushin 70b) explains this phrase (נשים דעתן קלות עליהן, literally, "women's minds weigh lightly upon them") as indicating lack of sexual inhibition.
Split into simpler sentences: Bruriah made light of the Talmudic assertion that women are "light-minded" Kiddushin 70b. Rashi there explains this phrase (נשים דעתן קלות עליהן, literally, "women's minds weigh lightly upon them") as indicating lack of sexual inhibition.