Here is the trick to writing strong female characters:
Write your women unique.
We need frumpy housewives to stand beside femme fatales and for both of them to be equally valuable to the narrative. We need fine ladies in sparkling gowns and we need rough tomboys in stained overalls. We need women who spend five hours on their hair and women who shave their heads. We need ladies in politics and ladies on the battlefield. We need adventurers and we need beaurocrats. We need women who are amorally machiavellian and women who are dedicated to a code to the point of fanaticisim. We need tall fat women and short bony women. We need black women and white women and brown women.
When all your female characters stand together, they should create a beautiful collage of opinions, colours, outlooks, sizes, and paradigms. They should agree on some things and be willing to fight it out on others. They should each be different.
When none of your female characters are comfortable in dresses, you have a problem. When none of your female characters can handle themselves in a fight, you have a problem. When none of your female characters are interested in romance, you have a problem. When none of your female characters are focused on their careers, you have a problem. When none of your female characters want to have children, you have a problem.
And when those “nones” become “all?” You still have a problem.
Real women are unique. We come in every single variation you can possibly imagine. We’re all strong in different ways and we’re all weak in others. We all value different things. We all have different dreams, different fears, and different desires.
Strong female characters aren’t a template. Strong female characters are a rainbow.