The posture you use in your golf swing is going to be determined by how you use your arms.
Adjusting Your Golf Posture Based on Arm Movement
If you are swinging your arms straighter back you are going to want a more upright posture, you are going to be standing taller and closer to the ball. Your weight will be distributed more on the middle of your feet towards your heels.
For a woman you are going to have to pay attention to your breast size. If you are a large-breasted woman you are going to have to stretch your arms out more in front of your own body to get you out of your own way. I will caution you that has the tendency to make you lift your arms up and take the club back to the outside from that setup.
You may decide that a one-plane golf swing is better for you. In a one-plane golf swing what you do is bend more from the hips. You feel more out over the ball. It is as if your abs are going back to your spine. It is not something where you stick your rear out where you get an arch in your back, it is always abs to the spine. That gives you muscle and bone support and that way it will not hurt your back.
When I do this you can take a little dangle test. The weight is on the balls of my feet, my arms are hanging nicely from my shoulders, I do not have my arms outside my shoulders, my chest is not really in my way, I have a lot of freedom in order to swing my arms across my body.
So when you are doing a one-plane golf swing, make sure that you bend over. One of the things that is real important with these posture tips I am giving you is that once you choose an arm swing you have to get into the posture that is going to make that arm swing work. If you decide you are going to swing one-plane but you are going to set up upright it is not going to work. You are not going to be able to find the ground properly.
Make sure that once you choose if your arms are going to go across your body it is very important that you are bent over. Some people stand a little upright and then they go down at impact, that is also an option but it is a lot more difficult to do with consistency. I am going to advocate that if you are going to play one-plane golf, which I really think is a great way for women to play, bend over more at address, arms hanging from your shoulders, weight on the balls of your feet, feel balanced.