I wonder if the brackets were not around the word female if it would be considered as offensive. Regardless it was a stupid thing to put on there. I don't even get why they added "female" to that sentence.
um, read it more carefully. It's saying women are a perk, then clarifies by saying that the women in question will be the ones serving drinks.
Paraphrased:
Perks:
* women: they're there to serve drinks.
The problem is not the "(female)" bit, it was the fact that the existence of women is reported as a "perk". Because after all, women are just objects that exist to serve drinks to men.