Yehudayona, I did not say it was ossur — I said it’s a good thing to have separate sitting. At Shabbos meals at home, it’s more difficult to have serarate sitting for a number of reasons. Plus, the women tend to show up there not as dressed up. However, I have been to Shabbos/Yom Tov meals where I felt uncomfortable because of the presence of overly fancy ladies.
And, yes, it is not tznius for married women to be dressed-to-kill.