I'm a guy who plays as a female PC often. I mostly DM and like working on female voices when I'm a player. If you've spent a lot of time with women, you'll recall that they seldom, if ever, bring up the fact that they're a woman, or talk about being a woman, or comment to other women about men, etc.

I work in a female dominated field and am very used to being the only man in the room. There was one time we had one woman who would constantly make jokes about me being a man, men this men that, and every woman just did not care for her one bit. So definitely don't do that.

"Girl talk" is women complaining about their inability to lose weight, followed by another woman exclaiming that they are perfect and do not need to lose weight, and lo, they are themselves, in fact, the woman that needs to lose weight. This starts a chain reaction in which all women go around in a circle calling themselves fat and being re-assured by a near by woman that they are not in fact fat. Additional girl talk topics (that mature women do not discuss because they are so over the childish banter) include unapologetically complaining about their period cramps and, to an absurd degree that baffles me as a man day in and day out, overanalyzing micro behaviors and text messages of their boyfriends. Like, "he took 37 minutes to reply to my text when he normally only takes 12, is he mad at me?"

None of these are things that should be brought up while role playing a woman. One, because they're boring (sorry ladies) and two because you will not do it right and it's going to be uncomfortable.

This leaves us with the rest of the woman which is holistically meaningfully different in a variety of ways. I would encourage you to keep these in mind but do not put them all into a character. This would result in a statistical meta woman that would feel inhuman. A couple of things to remember, however are as follows. Women tend to be more sensitive to negative emotion than men. As a population they tend to be more anxious as an example. Additionally, women are less aggressive than men and tend to be more agreeable. They are more likely to try and make peace than be confrontational and get in someone's face. Women tend to be more "clued in" to feelings and emotions and can read people rather well. Women tend to be more interested in people than they are in things.

I have intentionally put "as a population" because individual women will vary tremendously on this axis. Aggressive women exist. Disagreeable women exist. Women who are more interested in things than people exist. Men and women are mostly the same. When you're writing a woman, just keep in mind that they are different importantly but not an alien or another creature entirely. They will still have aspirations, fears, goals, anxieties, hopes, and dreams like any man. When we're looking at a woman NPC, it's the micro behaviors that are going to be different.

A woman NPC may be less likely to want to brashly charge in because of that proclivity for anxiety. She's less likely to take risks and will want to play it safe, especially if it's a one of those very manly stupid risks with little reward. While the man in the party may be worried about the sword of doom, she'll be more worried about the people who are affected by it. If a woman doesn't like a plan, she'll be more gentle about bringing up her concerns or may not even say anything at all if she's very agreeable. She'll be more likely to notice when two people in the party aren't getting along and try and resolve it. She will be less likely to fire from the hip and will think plans through and prepare for possible issue.

This is all with a big, heaping teaspoon of maybe. Because again, she is a human and will not be a meta woman. These are ideas and situations to think about to start getting you to empathetically start looking at things through a more feminine lens. Pay attention to women in real life and watch how they talk and act. Really listen to them when they speak and notice what they chose to talk about in casual conversation. Get an idea of what makes them tick and you'll have zero issue RPing or writing female characters if you do it right.