Just so Krsna can experience loving reciprocation, cooperation in a "two-way" exchange with another, Krsna divided Himself into two, Radha and Krsna.
And when Radha and Krsna act together in one spiritual Bodily Form, they are Lord Caitanya Mahāprabhu.
Srimati Radharani is not jiva-tattva, which means She is not an individual jiva-soul expansion from Krsna like us, no, She is non-different from Krsna, being His direct expansion.
Love can only exist when there are two individuals reciprocating with