Look man, from a technical language point of view there is nothing whatsoever wrong with calling people 'females'. However, by speaking to such people face-to-face you quickly learn that basically not one likes to be called that. The reasons are subtle, and frankly not very important. But the fact remains that calling people 'females' is now seen as a sign that you don't understand or respect them - on the grounds that you are using a phrase that you've been asked not to use. Just say 'women' instead.