So, now that you probably think I'm an arrogant feminist twat who's ruined your novel, let's talk about stuff you should do.
Women! How do they work?
Understanding a female character requires understanding people. This may require you to leave your desk and talk to actual humans face-to-face. If you've gotten into writing to avoid people, or you're unwilling to do research by talking to the sort of people you're writing about, put down your pen or consider quitting. Writing fiction, whether that's sci fi and fantasy or the highest literary work, is about people. At no point should your characters come second to your plot, and if basic to intermediate research about your population/character/history makes you uncomfortable, stop writing about your topic or change it. This is harsh advice, but it needs to be delivered, based on both the traditional and independent publishing industries' output.
Instructions unclear? Dick stuck in keyboard?
Right, so--women. Make them real people. Your female character is not your substitute best friend, nor your substitute girlfriend, nor an alternate version of you. She is a person who lives in your fictional universe. She has little things she likes, such as chamomile tea or the way cotton ankle-socks feel or the way fresh snow looks. People are built of little details and tiny scraps of history. Grand gestures and career plans are fine, but the way her little sister looked when your character broke her toy train when they were both children matters more. The way your character surprised her mother on her birthday matters more. You don't even have to write these things in (though writing about them for practice might not hurt) to imply that they exist.
Here are some elements you could consider adding to a character--if they fit, that is. Ask these questions and try them on for size.
Has your character been injured? Seriously? Have they got a disability? That could be interesting. Physical challenges are much more intriguing than super-magical competence powers. Sometimes they're even a trade-off for magic, but they don't have to be.
What is your female character's motivation? Does it solely revolve around one person, or two? If it does, try to explore her motivations from her perspective, in a way that doesn't involve family or romance.
What are her favorite things? What does she buy at a market or grocery store first? What are her small indulgences or her vices?
What's the meanest thing she's ever done, the smallest evil? I don't care about saving puppies. I want to know about that one time she kicked on and it let out the saddest whimper on the face of the earth. I want to know what keeps her up at night.
That should give you a starting point. Now, enough talking. Go read some good books with female characters. If in doubt, ask some women. And above all else: practice, practice, practice. We won't eat you alive, as long as you keep trying.