The basic rule of thumb is that anyone who gets upset with you using the word female isn't worth your time. If they're really going to get upset about you using the word female then they're probably going to get upset about a lot of other trivial things as well and that's not the sort of negativity and bitterness you want in your life.

I've switched to Lady for a lot of descriptors that I used to use Female. And a lot more They. Or just a physical description, like the person with the dark hair.

Edit: I'm probably trying harder than I need to. I just want to accommodate people.

Let me break down the explanations given, because most of them boil down to this:

As a noun, yes, because it's mainly used in biology like that ("A hawk female") and thus can come off as dehumanizing. As an adjective: No ("A female cashier", "A male cashier")

People that say 'females' out loud in public are quickly assumed to never get laid. It's okay to use when talking or writing about science topics and such.

How about: "The weaker sex" instead?

Friend, people will get offended by anything and everything. Didn't worry about it. You just be you.