Pac Man, MDD, perhaps it is the shitah of the Arizal that they didn’t dance, but chazal say they did in gemoro Tannis daf lamed alef omud alef.
Both in the mishna and in the gemoro, neither Rashi nor Tosefos brings any indication that the young women of Jerusalem were doing anything other than dancing. (I just looked to be sure).
I’ve learned the Meiri’s interpretation of this in the past, and he doesn’t indicate it was anything other than dancing either. In fact, if I recall correctly, he says they would dance and call out to the prospective husbands ‘kfi ma shemargishos beotzman’ according to how they felt about themselves in that situation.
The Chasam Sofer in Toras Moshe on Parshas Veyeilech also indicates they were dancing, as the gemoro says.
Some say that because of the nearness to the deprivation of Tisha B’av, there was little chashash of losing self control. (Brought in Sefer Hatodo’oh).
So – we have mishna, gemoro, rishonim and achronim indicating that they were indeed dancing. Now, I’m not going to say this means that everyone should interpret it that all simcha dancing should happen without a mechitzah – obviously. But I will point out the clear kal vechomer that if seeing women dance was permitted for the purpose of shiduchin, seeing them eat would seem to be obviously mutar.
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