jakyweb:
The problem is not intermingling.
It is when the 15-19 year olds that went to the wedding as members of the yeshiva decide to “hang around” when the girls all enter the men’s side to watch.
Should there be men dancing for the Kallah? Yes, it is a minhag Yisroel.
Should the teen girls and boys be watching each other (when the boys are not even close to being ready to get married)? IMHO, no.
Histaklus is Assur, and teen boys in yeshiva have enough problems as is.