Holland to Belgium (work and rights)

Does a Dutch citizen lose their pension and other important financial rights when they opt to work and live in Brussels? It is not an xpat job but one they found themselves. She is afraid she will lose all her rights in her homeland, Holland. How does she go about keeping them as long as possible? What are the loop holes? Where can we get this information? Love is calling her to Bxl but fear of losing everything in Holland is keeping her from moving. Thank you for your help.