It's probably significant that all of us were girls at that same age....yet even we can't remember what was going through our minds and emotions.....
Team sports are particularly valuable for girls...to get them over just exactly the kinds of problems you've run across: accepting public "criticism" (read: coaching) without taking it personally, co-operating with team members even if you don't like them, and the like.
My experience with my daughter and her friends taught me to NOT pander to their dramas and clique-ishness. (I'm fortunate that my daughter is pretty pragmatic.) Keep it businesslike and informative. Deal with them as young adults, not children.
Period whining? Sympathize that it is a bother...but remind them they'll be going through this once a month for pretty much the next 40-50 years, so deal with it.
Not getting along? Full team 'lecture' -- your here to play b-ball, not have a tea party. Team comes first, and the players are here for their skills, not for a social club.
Does this sound harsh? Not if it's put in a caring, but firm way. The young ladies love a good drama, and Mommy-ing them will only exacerbate things.
You've got a chance here to help raise women....not delicate little flowers. I bet your just the one for the job!
Good luck....and carry Midol....for ALL of you!
---------------------------------
From 'Nice Guys Finish Last' by Leo Durocher:
Baseball lives at the center of a never-flagging whirl of irreconcilable opinions.