Does calcium supplementation prevent postmenopausal bone loss?

No. But it will enhance bone remodeling, and if on bisphosphonate agent, it will potentiate it's effect as shown in a recent study. Concomitant vitamin d is recommended. Talk with your doctor.
See your MD. Usually you want to develop a combination of calcium and vitamin d to help prevent osteopososis. You first need a baseline to see if you are at risk.Then your gyn or endocrinologist can help you determine what is best for you. Good thinking ! good luck.