It's important that your motorcycle gear includes armor for protection in the event of a crash. While many jackets come with armor already built into the shoulders and elbows, and sometimes a removable back pad, this padding can shift during your ride and become uncomfortable. A separate back protector might be a better solution.
You'll want your back protector to be one made especially for women. It will have a tapered design that conforms to your body and fits a shorter torso. It isn't bulky and can be worn under a jacket or other clothing. No one will even notice you're wearing it.
Women's back protectors are designed for comfort. Adjustable shoulder straps and an elastic belt that fits securely around your waist will keep the protector in place. Venting on the protector allows airflow to keep you cool.
For more protection, you can add a chest protector. You can find some models that Velcro onto the straps of your back protector for complete armor protection.
Another protection option is an armor vest. Tailored for a woman, the vests are shorter than the men's version and come with adjustable Velcro straps for a proper fit.