Argh! finally, someone whose horse is behaving the same as mine!!
My mare is turned out with a 4yo gelding, and pays no attention to him what-so-ever when my gelding and his companion is out next to them. She squeals when they come near her and kick out (both ways) when they go to touch noses with her.

She has been on stroppy mare supplement for a while, its only chilled her out a little bit, still get squealing from her though.