To understand Radha correctly you need to somewhat understand the mysteries of the ecstatic experience of spiritual love. Krishna and Radharani playfully married once, as children sometimes do. They did not marry, however, because their love is more primal, profound, and unbounded than what wedded love facilitates. Wedded love is a very elevated type of divine union with the Supreme Personality of Godhead, yet in marriage the intimacy and spontaneity is not limitless. Some limitation is imposed by the sense of that husband and wife naturally acquire towards one another. This sense of duty is beautiful, but the highest type of love is even more beautiful. It is so profound that it requires no sense of duty and flows absolutely spontaneously breaking all things that stand in its path. Thus the pure transcendental love that Radha and Krishna enjoy on the highest level of bliss expresses itself in the form of being paramours, not being husband and wife.