Well, she would be right, why did he chose to use that rebuttal of all things? If a guy had said something similar, I bet you any money your friend would not have said that in relation to his job.
He went right for her occupation, which is predominantly occupied by females, and made out it was a stupid boring job, y'know, 'for girls'.
edit: sure, I can't prove he wouldn't have said something similar to a guy in relation to his job, but just from the fact that he went for an occupation that is mostly occupied by females, and is to do with personal upkeep/vanity, it does sound like he was being quite sexist there, as if she has a stupid girl job that is only about trying to make yourself look good, when in actual fact, it's a skilled occupation, sometimes highly so, that is basically a necesitty for people in this day and age, that is, unless you are a super genius who can give themselves good haircuts without any training, haha.