nobody is happy with just being a person to others anymore. It's not OK to be another head in the crowd...
...you can't know everybody and it's honestly not worth trying unless you have the time to spare or will be interacting with the person consistently
That's must be why so many people are obsessed with their identities. Getting to truly know a person takes time and constant interaction, but if you put a lot of emphasis on what you are rather than who you are, then you can get anyone to know how much of a special snowflake you are as a strong, independent (race/gender/sexuality/othernonsense), and do so in less than a minute. The problem is, that they're reducing themselves to traits that are supposed to be trivial, and are not supposed to define a person.
And if everyone is a special snowflake, then nobody is.
For what it's worth, I can't stand hearing women being called "females" either. Not for the same reasons, I think it just sounds stupid. I don't think "dehumanizing" is the word she's looking for, as that's basically a definitive human word. Maybe "depersonalizing" is more accurate, since it just washes over any individualistic qualities of the person in question.
Therein lies the problem, I suppose, because nobody is happy with just being a person to others anymore. It's not OK to be another head in the crowd, it's terrifying to them. It's just the way it is, you can't know everybody and it's honestly not worth trying unless you have the time to spare or will be interacting with the person consistently. Still, treat everyone as well as you can and be humble.