Is there an inyan zecher lachurban for a woman not to wear all of her jewelry? If so where is the mekor? And is it a chiyuv (obligatory), or is it just proper to do so?
Based on the Gemara (Bava Basra 60), the Shulchan Aruch (Orach Chaim 560:2) rules that a woman must not wear all of her jewelry, in order to recall the destruction of the Temple. [Poskim dispute whether or not this applies even on Shabbos — see Birkei Yosef and Mor U’ketziah.] This means that she should ensure that at least one type of item of her jewelry is not worn (Mishnah Berurah 8).
However, the custom today is not to be particular concerning this halachah, as the Mishnah Berurah (in Biur Halachah, 560, s.v. vechen, in the name of Chayei Adam) points out.