What’s important when choosing a bike.
Relationship is one of the most important components – relationship with your local bike shop. Not just for the purchase but also the fitting and servicing.
Test ride as many bikes as possible. Ignore price range initially; start at the top then work down, you will then know what quality is. Every bike handles differently, so take this opportunity to ride a variety of frames (titanium, carbon, steel, aluminum)
Don’t worry too much about fitting, once you have picked your bike you can then concentrate of adjusting it to fit your correctly. I.e. swap out stems, bars, saddles to set up the bike so it's just perfect for you.
Take a friend who is also into cycling
Typically, a woman's torso is shorter and her legs (especially the femur) are longer. Our hands are smaller and our shoulders narrower. We even carry our weight (center of gravity) in a different place. So find a good shop that will acknowledge these differences and take the time to address them in your fit. A shorter top-tube or compact geometry, a narrower bar, and shimmed levers will all help make the bike fit your unique needs