As for things getting along...Sally Anne is a pureblood as far as most of wizarding society goes. She should probably be friendly with Michael since they are both former Ravenclaws and (hooray!) he's half-blood. I don't know if she knows Pansy or not. The Warringtons are not stinking filthy rich but they are pureblood so maybe they bump into each other occasionally.
Adrian should probably continue hating Michael and keep trying to get Pansy in bed. He's such a simple creature *pets*