Gee, she KNOWS you wanted to go...and thats bad enough...
in reality...if you went anyway you'd be in trouble and if you didn't go you would be in trouble...
kudos for telling the truth...but maybe next time lie or just tell your boss no in the first place, then go home tell the GF and then probably get great sex for choosing her or the $5 whores...
then again, if I remember right, your chick is psycho but paying for everything...right?