I have to admit, this story had me scratching my head.
On one hand, the *actions* of the girlfriend and her friends were horribly inappropriate, but I fail to see what was wrong with their mode of dress. I went to a chamber music concert last night and sitting near me was a woman with dreadlocks and multiple facial piercings. Should she have been thrown out, or looked down on, simply for that?
I also think that a company that would fire an employee because of something their friends did outside of the workplace and at an event where (I assume) no-one was officially representing the company is a place to be avoided like the plague. I think the letter writer is better off without the boorish girlfriend *and* the controlling boss.