At some frum Simcha's [or "Smachot" if you prefer] the men dance on the men's side and the women on the women's side.
At other simcha's - only the men dance and the women watch.
[And then there are the "dinner dances" of some hyper MO shuls where there is coed dancing.]
At my Bar Mitzva, we had everyone dancing, men and women in separate circles. It was GREAT!!! But BY GOLLY, someone forgot to put a mechitza between the sexes, so my frummy-holy female relatives did not join the dancing. A REGRETTABLE oversight I must repent for [I just became a Bar Mitzva and was already doing aveiros!!!] and was rectified slightly at the Bar Mitzva of all of my sons B"H where we had lots of great dancing with a mechitza. Back in the 1980's, mechitzos at simcha's, like hair covering for married women, were less fashionable than it is today. BARUCH HASHEM for עליית הדורות!!!
But when do you have a simcha when the women are dancing and the men aren't??
Yet, at the very first national simcha of Klal Yisrael, after Krias Yam Suf, the ladies danced and the men didn't!!!!????
WHY?