i bred my bullmastiff on the 10th and 12th day of her season.everything was fine she presented herself for the stud and everything was fine.i want to know should she be still standing for my own dog still at the 18th day.my dog has been castrated.

my girl flirts for days after ...quite normal

Bitches often flirt with their resident "boyfriends" throughout their entire season - this is neither unusual nor a sign that your "approved" matings were unsuccessful.   This is often a cause for secondary matings taking place (where there is more than one sire in an actual litter) - although thankfully not an issue as your boy's "been done" ;-)

Teri