How many pnms get dropped

There are very few pnm's that get dropped from all houses. It does happen, but the vast majority of pnm's that leave the process drop of their own choice.

Some sororities must make heavier releases than others at every round, so while some choices are eliminated for a pnm, there are still others left for her.

As far as "an above average convo", well there are multiple conversations throughout the week, so it's about meeting more members each round and having consistently good conversations each time.

A sorority invites pnm's to pref that they can see as sisters. That's all I can tell you.

Literally everyone gets dropped. Then you go and prove your worth by fighting a war eagle. The ones who survive get to select their houses for pref. Good luck ladies